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Revisiting the Twin Comanche: A Flight review of the PA-30

Revisiting the Twin Comanche: A Flight review of the PA-30

After a 30-year gap, the author gets a chance to fly another Twin Comanche and realizes he rather likes it.

Its name rather gives the game away with this iconic light twin. The Piper PA-30 Twin Comanche design started with the single PA-24 Comanche, a laminar-winged rocket which itself was a breakaway from the sturdy but slow aircraft that Piper was famous for at the time such as the Cub, the Cherokee and the Apache. 

Beech had taken the GA world by storm with the Beech Bonanza, and Piper had to up its game—literally. In order to keep up, along came the PA-24 in 1958. But when the Bonanza begat the Twin Beech and subsequently the Baron, the idea of giving the PA-24 to Ed Swearingen to re-engineer as a twin was a truly inspired one. 

The result was an aircraft which could fly faster than the much later Piper Seminole on less horsepower and yet lift more. And despite losing some effective wingspan due to its twin-engine installation, the Twin Com has only 9½ inches more span than the single.

The Twin Com first flew in 1963. It was and is a fantastic little aircraft able to fly at 160 knots below 10,000 feet, burning just 9 U.S. gallons a side on a combined total of 320 hp. Turbo Twin Comanches are particularly fast at altitude, typically cruising at 195 knots or 225 mph at 20,000 feet. With speed mods to the wings, fillets (i.e., fairings) and engine nacelles, this figure climbs—speeds of 200 knots-plus on Twin Comanches are easily doable. 

Despite their success, Piper was out of its comfort zone with the Comanches, and when a flood destroyed the Lock Haven factory in 1972, the company possibly used the excuse to stop production when only just over 2,000 Twin Coms had been built. The counter-rotating PA-39 was just getting started, with not even 200 leaving the production line. 

After the recession in the 1980s/1990s, Piper looked at its existing stable of twins and considered restarting twin production. But it was reckoned that the labor-intensive construction of the Twin Com would result in a cost of at least $1 million per aircraft in build cost alone. The much cheaper but less capable Seminole was brought back into production as a result. 

Nowadays PA-30s and particularly the small handful of PA-39s are cherished aircraft with a keen following and strong owners groups who make a point of using the types’ long legs to arrange fly-ins all over the world. 


A bit of a handful

My first experience of the Twin Com was when I did my twin rating in 1985. At the time, both the aircraft which I hired (G-AVVI and G-AXRO for the spotters) were in commercial use as charter aircraft at London Southend Airport (EGMC). 

I remembered finding the performance a big leap from the Piper singles that I had flown in. I listened intently to the stories I was told of the infamous laminar wing, how the aircraft could fall from the sky if you flew it too slowly or by the seat of your pants without paying attention to the airspeed indicator. 

In aerodynamic terms, up until development of the Twin Comanche, Piper had been very much a one-trick pony, using the old Cub airfoil on its subsequent faster aircraft. These high-lift wings convert airspeed to lift much more readily than with laminar designs. If you’ve ever wondered why a laminar-winged aircraft cuts through the gusts while the average high-lift-winged Piper will have your head impacting the roof, now you know.

The one big disadvantage with a laminar wing is that its stall is usually much more dramatic than with a traditional airfoil such as a Clark Y. I found this out flying into Le Touquet (LFAT) in northern France not long after getting my twin rating. I was coming into land on the now-disused southwest runway and had reduced my speed to minimum approach of around 80 mph—well below the single-engine safety speed of 105 mph—because I had already committed to land and the runway was short. 

As I flared to land, I encountered negative wind shear and the aircraft felt as if it literally fell out of the sky. I managed to firewall the throttles to cushion the impact—but the landing was hard enough that once I had taxied clear, I stopped and got out of the aircraft to examine the main gear to make sure there wasn’t any obvious damage before continuing. 

I got away with no damage, but the incident left me shaken.

With the above experience still in my data bank after all these years, I was intrigued to reacquaint myself with the Twin Com. I’m in my 50s now, so not as sharp as I was, but I’m experienced on swept-wing jets and various laminar-winged high performance aircraft, so I was expecting to not be unpleasantly surprised by the Twin Com. 

Then again—you never know, do you? 


An introduction to N25PR

Owner Mark Hadley showed me around his immaculate 1967 Twin Com Turbo B at North Weald Airfield (EGSX), complete with its beautiful and original blue-and-white paint scheme. You can tell it’s a B because of the extra side windows and the facility for an extra row of seats. 

The first thing that strikes me is its size—so much smaller than the beefy Apache and Aztec, and smaller still than the Seminole trainer that came later. 

A Twin Com has 40 less horsepower and 200 pounds less MTOW than a Seminole, but it can propel a similar load considerably faster. No surprise then that it is at least 20 percent better in every way than the old Apache that it replaced.

Climbing inside a Twin Com is the aviation equivalent of entering Doctor Who’s time machine, TARDIS; the toy-like airplane reveals itself to have a quite large cabin. 

It’s a serious machine in every way. Controls, levers and dials are in abundance, sprouting from the deep instrument panel. The windscreen almost seems like an afterthought, and the effect is akin to looking out of a letter box—until you get the seat position just right so that your eye height is halfway between bottom and top of the screen. 

The next thing I notice are the engines projecting out much farther forward than with many other light twins, so that you sit well behind the props. I’d imagine a World War II de Havilland Mosquito must feel a tiny bit like this. 

Once strapped in, the area around the front seats is actually quite roomy. At 44 inches across the cabin, it is 2 inches wider than a Baron, and even the rear seats can be occupied by two adults. 

Between the seats—a space wide enough for a traditional flight case—there are panels which lift or detach to expose emergency landing gear lowering apparatus, the fuel tank selectors and an archaic fuel draining setup, which I remember didn’t work very well. What you have to do is raise the panel and then pull each drain knob in turn and observe fuel flowing through a clear plastic pipe to see if any water appears. 

In reality, the pipes are usually covered in dust and grime and they also have an annoying habit of working their way inside the bottom of the fuselage which means the drained fuel exits inside the aircraft before finding its way through some or other gap and outside. Probably not a good idea to avail yourself of the cigarette ashtrays in the cabin. 

The most obviously unusual feature of this cabin, though, is at the bottom of the throttle quadrant: there project two overly large turbo controllers—verniers, like the throttle/prop controls from a Cessna—which are used to bring the turbos online at altitude; and, more importantly, which are used to wind them offline during a descent. If you don’t, you will overboost the engines. 

Out there on the wingtips are the optional 15 U.S. gallon tiptanks, which up the total fuel capacity to 120 U.S. gallons and, because of the cantilever effect of weight distribution, also increase MTOW by 125 pounds to 3,725 pounds. One-hundred and twenty gallons divided by 18 gph equals 6.6 hours, providing a 1,100 nm range on 320 hp! And for the turbo version it’s 1,300 nm-plus! As I said, a serious machine in every way. 


Two versus one

The starter, mags, fuel pumps and generators are a line of toggle switches at the base of the instrument panel. Engine starting is classic fuel-injected Lycoming: crack the throttles open, hit the fuel pumps until you see an indication of fuel pressure, pull the mixtures to lean, make sure the generators are switched off, crank each engine in turn after switching the mags on; and, as it fires into life, bring the mixture levers up to full rich. After startup, check oil pressure rising and bring the generators online. 

Very straightforward it may be, but there is always a sense of occasion starting up a twin—I remember thinking as a twentysomething that I had finally arrived when I soloed one of these aircraft, and that same rush is still with me more than 30 years later. 

I release the brakes with the chrome locking T-handle in the panel under the control column and allow the Twin Com to roll forward under idle power before checking the toe brakes. There is quite a bit of weight on the nosewheel due to those projecting engines, but the steering is actually light and progressive. 

A little care has to be taken about the geometry of the toe brakes—they are too upright for my taste; because of a running injury, my right foot can’t go less than about 70 degrees to my lower leg, and you can easily taxi with the brakes deployed inadvertently. I slide my feet down a little to stop myself. We are a long way under our MTOW, so the aircraft feels sprightly. 

The engine runup and pre-takeoff are quite involved and I opt to use my old commercial pilot checklist from the 1980s, which has been typed out and photocopied to death. But if it was good enough for the commercial pilots of the time, then it’s good enough for me. 

I advance the throttles fully forward and the aircraft accelerates well. The previously heavy elevator comes alive in the prop wash and I hold the column neutral as we gather speed. 

At 70 knots (80.5 mph) I raise the nose and the aircraft unsticks abruptly. I apply the toe brakes and then raise the gear with the tiny selector to the left of the panel. Gear retraction is normal. 

The airspeed indicator is pegged at 1,500 fpm before I bring the throttles and props back to 25/25 then sync the props by pulling one prop lever back and forth to locate which way slows down the “wah wah wah” noise; then keep going until the noise stops completely. From the ground the Twin Com sounds quite noisy because of its unusual exhaust pipes, but in the cockpit there isn’t as much noise as in a comparable single. 

As we break out of the circuit and head for the Essex coast I start to get a feel for the aircraft again after my 30-plus year gap. It feels like a larger aircraft than it is. The elevator is firm but correct for this type of airplane, roll control is lively and with high hysteresis in roll—or roll inertia—due to the wing-mounted engines. If you come from high-wing singles, this will take some getting used to, and you will find yourself seesawing in roll until you settle down. 

The Twin Com is actually lovely to hand-fly and I didn’t use the autopilot at all during our hourlong flight. Formation flying with the camera ship was pretty straightforward, although it was easy to get unsighted during the breakaway maneuvers due to all the hardware obscuring the view. 

The turbo controllers are used as follows: when the desired manifold pressure can no longer be obtained by advancing the throttles in a climb, you turn to the verniers and start winding them in until manifold pressure is restored. By 20,000 feet they will be all the way in and you will be flying at 195 knots (225 mph) or better. 

In the descent, the opposite is the best way to proceed—rather than abruptly disengaging the turbos, just leave the throttles fully forward and progressively wind the turbo verniers out until they are all the way back, then slowly retard the throttles. Yes, it requires a bit of work, but then this is a 50-year-old airplane.


One out

Next, we try flying on a single engine. I get owner Mark to feather our left engine as I keep control of the aircraft and allow the camera ship to fly alongside. 

The rudder is powerful and I can easily hold the out-of-trim forces with one engine shut down, although the use of rudder trim and a little bit of aileron trim means I can actually fly hands-off. Why aileron trim? Because a wing without the benefit of prop wash creates less lift—even a laminar one. 

Slow-speed flying is also predictable, as is the abrupt g break you get clean or dirty. Add power and the g break is accompanied by a wing drop of as much as 45 degrees. To stop it, just unload the wing with a shove of forward column and that’s that. All laminar wing aircraft that I have flown are the same as this.


Approach and landing

Back on the approach the Twin Comanche behaves itself, just so long as you remember to adhere to the correct speeds. I am having no problems going down, slowing down, and fitting into slower circuit traffic at North Weald. 

The aircraft is not particularly trim-sensitive, and the old fashioned, roof-mounted trim wheel feels instinctive as I progressively wind it backward for nose-up trim as we slow down, and then introduce progressive flap, then gear down (no trim change). 

I fly finals at 105 mph, remembering the old blue line safety speed from my training many years ago; then back to 90, then 80 as I cross the fence. Throttles closed at the same time as, but not before (laminar wing, remember) a small flare and we land on the main wheels in a flat attitude, quickly followed by the nosewheel. 

Some owners pump the main wheel oleos to the full extension to avoid this, but then the ride suffers on the ground. Running down along the hard at North Weald feels the same as the ride you get in a 1950s British sports car.

How much?

I looked at the U.S. market for used aircraft and PA-30s were all in the $45,000 to $120,000 price bracket. That’s pretty wide, but it reflects the cost of replacing two engines and two propellers in addition to the usual variations in condition and equipment. 

I couldn’t find a single PA-39 for sale—and that’s Situation Normal considering how few were made. 

A large (6-foot, 4-inch and 252-pound) friend of mine has been looking for a twin for some time to commute 600 nm at a go, and was looking at Barons and Cessna 310s, which have twice the burning/running costs of a Twin Com. He thought the PA-30 too small—but I think he might well change his mind when I arrange for a flight in one in the next few weeks.

A bit of a handful? Not at all; just don’t get slow.

Bob Davy is s commercial pilot and aviation journalist from London, England. He spends most of his time flying around Europe in Avro RJs for airlines and private clients. He has 15,000 flying hours in nearly 300 different fixed-wing aircraft. Davy knows he is lucky because he regularly flies three of his five favorite aircraft: the P-51, the Nanchang CJ-6 and the Pitts Special. (His other two favorites are the Hawk and Spitfire). Davy has been published all over the world. In addition to writing hundreds of flight tests, he has also written a novel, “In Case of War Break Glass,” which takes place in World War II and is loosely based on the life of Robin Olds. The sequel is underway. Send questions or comments to . 

Photographs by Keith Wilson

Destination: Miami

Destination: Miami

Though it is as beautiful and sunny as it looks on television, the city of Miami isn’t exactly like it’s portrayed. This is a city that’s best viewed in-person.

What I thought I knew about Miami, I realize now, has all come from the television. “Miami Vice,” “The Golden Girls” and “Burn Notice”—these fictional portrayals all shaped my idea of the city’s surroundings, its residents and its culture. I think I was more wrong than I was right.

When I started looking deeper, I realized why Miami is portrayed so much in films and on TV: it’s a huge hub for this kind of thing. There are more than 2,000 motion picture, music and video companies based in Miami; dozens of recording studios and sound stages; hundreds of freelance production crews; dozens of cable television networks.  

Miami looks shiny and new, and it is, relatively speaking. Nothing here is much more than a century old, as this port city was incorporated in 1896 with, surprisingly, just 300 residents. It’s a city that has made its name known—so much so that the former Dade County was officially changed to “Miami-Dade County” in the 1990s. 

Today, by some markers, Miami is considered one of the richest cities in the United States. With miles of picturesque boulevards and high-end shopping, hundreds of high-rise buildings and the most concentrated grouping of international banks in the country, this isn’t hard to believe. 

Set up for success

There is no shortage of information about Miami. In fact, it’s almost overwhelming how much is available. The 2017 Visitor’s Guide is a whopping 252 pages—and it’s one of a dozen free guides available on the Greater Miami Convention & Visitors Bureau website. 

With 22 regional visitor centers around Miami, this city was built for visitors. If you want to see the palm trees sway in real time, keep an eye on Miami through its seven live webcams. The information available online is abundant.

There are even mobile apps available for free (or nearly free; they cost a few dollars at most). With these apps you can get detailed information on the arts district, the parks, the airports and city transit, various historical sites and walking tours, locally recommended food, shopping and a lot more.

Local attractions

There are a few attractions that I think are musts when you’re visiting Miami. Here are a few of my picks.

Calle Ocho – By my count, there are at least eight cigar shops and factories on SW Eighth St. in the Little Havana section of the city. Even if you can’t tell a claro from a maduro, you can’t help but feel fascinated while watching a master cigar roller create an authentic Miami-rolled Cuban cigar. 

For a similar amount of immersion in Cuban culture with none of the nicotine, maybe order a cafecito (Cuban espresso, or Café Cubano) or stop in at El Rey de Los Fritas for a fast lunch (fritas, of course), and then walk down to Maximo Gomez Park to watch a game of dominoes—or maybe to enjoy that cigar. (I’m sure you won’t be alone.)

The Miami Circle – One highly unusual feature in the city is the Miami Circle, a prehistoric limestone building site that’s 38 feet across—in the middle of downtown, off Brickell Avenue. Though many at first doubted its age, the circle predates other East Coast settlements and is believed to have been used by the Tequesta Indians. Many Tequesta artifacts are viewable at the HistoryMiami Museum on West Flagler Street. The museum is several blocks northeast of the site, across the Miami River.

Biscayne National Park – This natural haven is within sight of Miami in nearby Homestead, Florida. This park is different than most: it’s mostly made of water. The National Park Service protects these shallow waters, coral reefs, marine wildlife and tropical hardwoods—there are no roads or bridges, and only one hiking trail.

Since the vast majority—90 percent—of the park’s half a million annual visitors enter the space by water, there is no entrance fee. There are, however, fees for special uses (overnight docking, camping at the two campgrounds in the park, etc.). 

The Deering Estate – Environmental enthusiasts can also check out The Deering Estate, a preserve in the village of Palmetto Bay, which offers hikes and science education for visitors. It’s a lot closer to the heart of the city (and a little easier to access than Biscayne National Park if you don’t have a boat with you). The estate runs a moonlight canoe tour, which takes paddlers across Biscayne Bay to a waiting campfire on Chicken Key. The tour costs $40 and is open to adults only.

Art Deco Historic District – Lastly, Art Deco architecture is a worthwhile sightseeing trip from downtown Miami across the causeway to the east end of Miami Beach’s South Beach neighborhood. Tours of all types—guided, private, self-guided—are available seven days a week through the Visitor Center. There are more than 800 buildings to see.

Other ways to spend your time in Miami might include beaching it—no explanation necessary—or window shopping at one of Miami’s many retail districts. For an indoor (read: totally air-conditioned) experience, look to the Brickell City Centre. 

If you want the full “I’m in Miami!” retail experience, the outdoor Bal Harbour Shops on Miami Beach are a fashion mecca. With an astounding number of luxury brands and an eponymous fashion magazine, I’d consider this a tourist destination in its own right. 

Upcoming events

Miami has several great events coming up in the first part of this new year. I’ve listed a few here, along with the dates. To find out more, see the Resources at the end of the article.

South Beach Jazz Festival – Latin, New Orleans-style and classic jazz music will be performed at various venues in South Beach January 5, 6 and 7. Branford Marsalis headlines this year’s event—it’s sure to be a big draw for a festival that’s just in its second year.

Miami Marathon/Half Marathon – This unique single-loop marathon has been running (sorry, I had to) since 2003. Since Miami is a Boston Marathon qualifier, it attracts 25,000 competitors from around the world—as well as 50,000 spectators. If you are in Miami on January 28 this year, you might want to be part of the cheering section.

Coconut Grove Arts Festival – A huge and highly anticipated arts festival occurs Feb. 15–17 in Coconut Grove. With fine art, food, music and performing arts all on showcase, it’s worth a trip to eat, walk and shop around. One-day passes are available for as little as $10 for this 55th annual event. 

Calle Ocho Festival – This event has the feel of a neighborhood block party, except it spans 24 blocks. The Calle Ocho Festival has 30 stages of music and its vibrant atmosphere makes it a true Pan American celebration. This year, the date is March 11. If you go, just know that it might be a little crowded: one million of your closest neighbors will also be at the party.

Flying in

Miami is a bustling place, and the Miami International Airport (KMIA) offers the largest quantity of commercial flights to the Caribbean and Latin America in the entire United States. It’s also first in international freight in the United States. There is a General Aviation Center at KMIA, and with customs there, it’s a must for international visitors. Many interstate flyers would probably look to land elsewhere, if possible.

There are a few other appealing options. The first is the Miami International reliever airport, Miami Executive Airport (KTMB). It’s located to the southwest of downtown, has 24-hour staff, three long runways and a helipad—and has about 500 operations per day. Fuel on the field averages around $6 per gallon at the time of this writing. 

Similarly, Miami Opa-Locka Executive (KOPF) to the north of the city is also a reliever for KMIA. It averages about 400 operations per day and lots of these are jets—which means the runways are nice and long. Fuel is about a dollar per gallon higher than at Miami Executive, though one of the three FBOs was comparable to KTMB’s prices. 

Miami Homestead General Aviation Airport (X51) is a little further south and west of the central city and is more set up for the DIY types, with self-serve fueling at a more reasonable cost (right around $5/gallon) and no tower. X51 has two paved runways and a turf strip along with 24-hour restrooms and lounge. Unlike KTMB, gliders aren’t restricted here, so parachutists, RC aircraft and agricultural aircraft are all in the vicinity; something to keep in mind.

Finally, North Perry Airport (KHWO) is located about 14 miles north of downtown Miami and 6 miles north of KOPF. North Perry offers four runways, a control tower, cheap Avgas ($4.25/gal) and a GA-friendly atmosphere. There are several flight schools at North Perry, so the traffic pattern(s) can be quite busy. However, you won’t have to dodge many jets; the airport is closed to aircraft over 12,500 pounds MTOW.


If you’re looking for a winter escape and like to be in the middle of the action, Miami may just be your ticket. It’s not all shady smugglers, dotty retirees and former spies; it’s oceanside beauty, mingled cultures and exquisite architecture. There’s way more to see and do here than I’d ever known if I’d stayed in front of the television.
Sources: miami-airport.com, miamiandbeaches.com, wikipedia.com, yelp.com.

Heather Skumatz is production coordinator for Piper Flyer. Send questions or comments to .





Miami International Airport (KMIA)


Miami Executive Airport (KTMB)


Miami Opa-Locka Executive (KOPF) 



Miami Homestead General Aviation Airport (X51)



North Perry Aiport (KHWO) 




Greater Miami Convention & Visitors Bureau



Miami mobile apps



Miami webcams




Biscayne National Park 



Deering Estate 



HistoryMiami Museum


Little Havana



The Miami Circle, Historical Museum of Southern Florida



Miami Design Preservation League (Art Deco Historic District)




Bal Harbour Shops 



Brickell City Centre



Calle Ocho Festival



Coconut Grove Arts Festival



Miami Marathon



South Beach Jazz Festival



Full Circle: Wind Dilemmas

Lessons learned about wind and mountain waves.

As I sit to write this, the major theme in my life these past few weeks has been wind. I say that because, first and foremost, we are right now involved in cleaning up our Florida horse ranch from the effects of Hurricane Irma—which, thankfully, amounted to only a half-dozen fallen trees and, literally, an infinite number of tree limbs scattered across our acreage. 

The second reason these past few weeks have involved wind is that I was concurrently producing an audiobook version of Harrison Jones’ nonfiction book “Miracle on Buffalo Pass: Rocky Mountain Airways Flight 217.” Reading for the audio version got me to thinking about experiences with wind-induced dilemmas from my own aviation past.

The book itself is an in-depth analysis and interview with nearly all the survivors of the Rocky Mountain Airways Twin Otter turboprop that crashed in a blinding blizzard at the very top of one of the most inaccessible spots between Denver and Steamboat Springs, Colorado on Dec. 4, 1978. 

We follow the passengers and crew through their experience, and then the bands of rescue personnel who mobilized immediately to attempt to locate the wreckage and any potential survivors before they would invariably freeze to death on that desolate mountaintop.

As the NTSB later concluded, the Rocky Mountain Twin Otter encountered an unforeseen severe mountain wave which, when combined with some airframe icing, prevented the commuter airliner from climbing above 13,000 feet (the MEA in that area was 16,000 feet) and the airliner was then gradually forced down into the terrain, just barely clipping the top of the mountain at Buffalo Pass. 

The first miracle was that everyone survived the initial impact with the crest of the mountain, but if rescue folks didn’t locate them quickly (no one knew for sure where they had gone down, and it was the middle of the night in a driving blizzard), none of them would survive.

As the NTSB pointed out in the accident report, one of the things that disguised what was happening was that the mountain wave the flight was involved with was quite smooth. With no wind-induced turbulence to tip the crew off, the initial symptoms of decreasing climb performance seemed to be more related to either engine power output or airframe icing. When the pilot in command is not understanding why something is happening, it’s far more difficult to come up with a reasonable plan to correct the problem. 

My own experiences with mountain waves were certainly nowhere near as dramatic, but they were personally attention-getting. Being more of a flatland pilot, my initial exposure to the effects of wind across undulating terrain came from those small bumps in the earth around Kentucky and West Virginia that we Easterners call mountains.

About 50 years ago I was skittering around Eastern Kentucky in, if my memory serves me correctly, a Piper Pacer with a 90 hp engine. It was a breezy day—nothing too outlandish—and I was giving a student some dual in the art of crosswind landings at an outlying grass field we often used. 

After a half-dozen acceptable takeoffs and landings in the quartering wind that was 20, with maybe gusts to 25, we left the airport for a little local flying up higher to get away from the bumps. 

After a few steep turns and whatever else I thought the student could use, I figured that we’d top off our day with a simulated engine failure, then head back to the barn. I chopped the power and announced: “Engine failure.”

The student picked a field below in a reasonably wide valley between two rows of hills, and set up an approach to a large pasture. Down to about 300 feet everything looked fine, so I announced, “The engine is working again; just go around and head back to the airport.” The student complied.

Sort of. 

He did everything right. So did the airplane. But Mother Nature did not. The student pushed the power up to max; 90 horses surged into the prop, and he turned us toward the airport that was on the far side of the next ridgeline. But we were, I figured out later, on the leeward side!

At max power and max climb speed, we were barely holding altitude—and the ridgeline in front of us was getting nearer! I was getting less comfortable with every passing moment, until I finally said, “I’ve got it.” 

Suspecting there was something now wrong with our engine, I did a snappy one-eighty to head back for our simulated emergency landing field—one that I figured we might need for real. Partway back—and, it turns out, away from the effect of the downward wash of wind over the ridgeline—we began climbing normally again. We climbed to a higher altitude, then crossed that ridgeline far above the mini-mountain wave effect beneath us.

Many years later I was in a light twin flying between northern Colorado and Montana, where there are some real mountains by anyone’s standards. It was a breezy, clear day and I was flying at the MEA, enjoying the view of the ridgelines and canyons that passed below. 

What I noticed first was the airspeed slowly trickling away as the autopilot kept pitching us up a little more as it tried to hold our altitude. Again, my first thought was that something was wrong with the power output from the engines, or at least one of them.

Yet all the engine gauges were middle of the green. They sounded fine, too. So what could be happening? It took me a few moments to see the obvious: the line of higher mountains to the northwest of my location were at a right angle to the prevailing wind. We were apparently in a downwash of wind from them. 

I requested a higher altitude from ATC, pushed up climb power and while the rate of climb was a little lower to begin with, a few thousand feet of climb later, the performance numbers went back to normal as we got above the downward effect of the distant mountain wave.

But don’t think that only smaller airplanes are susceptible to this sort of wind-induced dilemma. About 30 years ago I was the captain of a Boeing 737-400 headed westbound to San Francisco over the middle of the biggest rocks in the Rockies. We were at FL310 on a windy day, with our ground speed being clobbered by the constant westward flow. Still, the sky was smooth—so all was well, right?

First clue: the sense of the airliner trying to climb, the autopilot rolling in nose-down trim and pulling off engine power to keep us at altitude. I commented to the copilot something insightful, like, “What the hell?” 

I disconnected the autopilot, reduced the power on both engines until they were back at idle—and we were still being propelled upward at over 2,000 feet per minute! It was hard to believe what the gauges were saying. I pulled out full speed brakes, and still we were climbing! 

The copilot told ATC that we couldn’t hold altitude; that we were being pushed up. We got to 35,000 feet and I began to seriously worry because, even thought the sky was still smooth, if we went much higher the air would be (in a manner of speaking) too thin to keep the wings from stalling—“coffin corner,” it’s called.

Then we hit the turbulence, which started at severe and quickly got worse. Our big Boeing airliner was simultaneously being pushed upward and churned all around the sky! We needed to get down—quickly—before the wings decided to do the job for us. 

I was just about to call for gear down (at this airspeed, it would have probably done some gear damage) to get more drag to stop us from climbing when, in the blink of an eye, the washing-machine sky we were in went dead calm.

We had popped out of this mountain wave-induced wind machine at 35,400 feet. We stopped climbing, the airspeed began to drop, and I then pushed engine power to a low cruise setting. After coordinating with ATC, we turned off our route that had us headed toward the highest mountains and eventually drifted back down to our assigned altitude of FL310.

So that’s what I spent Hurricane Irma doing: narrating the book “Miracle on Buffalo Pass,” which is about the results of a wind-induced accident, while listening to the winds howl around my own home. 


Like an old captain once told me nearly 60 years ago, “Son, don’t fool too much with Mother Nature. She can win anytime she wants to.”

Editor at large Thomas Block has flown more than 30,000 hours since his first hour of dual in 1959. In addition to his 36-year career as a US Airways pilot, he has been an aviation magazine writer, a best-selling novelist and the owner of more than a dozen personal airplanes. Send questions or comments to

Evaluating Bifocal Sunglasses for Aviation

Evaluating Bifocal Sunglasses for Aviation

A professional pilot tested Dual Eyewear’s bifocal sunglasses under multiple conditions with good results.  

I've always had a difficult time finding bifocal sunglasses that combine utility, comfort and style. Most pilots needing corrective lenses wear untinted bifocals with flip-up sunshades or use expensive prescription-grade tinted lenses; some, like me, try attaching unreliable hydrostatic appliques to regular lenses or just suffer through squinting in sunlight.

Then I came across Dual Eyewear’s bifocal sunglasses in a print advertisement and wondered if they might have solved my problem. The company has engineered an aviation collection of six different 1.5/2.0/2.5x bifocal styles with three color choices of shatterproof and scratch-resistant lenses that provide 100 percent UV protection. Sounded good enough to try.

I field-tested three of the five available aviation bifocal sunglass products. 

Acting the role of test pilot, I checked them for functionality, style and durability; I also investigated their compatibility with digital avionics displays and gauged their comfort in a working pilot’s most challenging real-world condition: while wearing a headset. 

I evaluated each pair of glasses in my single-engine plane as well as while flying an airliner, driving my car and even while mountain biking—and the results were fantastic in all cases.

First, I tested the modern-style AV1 with the gray lens, then the green lens in the classic World War II aviator-style, AV2. But my favorite was Dual Eyewear’s NV1 style with a bronze lens. 

I found the height of the bifocal line on all three pairs was perfect for allowing a corrected view of the up-close instrument panel, tablet, or GPS and simultaneous views outside—without needing to nod up and down to refocus from inside and outside. In addition, I had no problems reading various color digital avionics displays and tablets while wearing these bifocal sunglasses. 

Thin stainless steel frames fit nicely under various aviation headsets (I tested them using two different headset brands) without the throb that often comes when thicker-framed arms are pressed against the temple. 

Dual Eyewear bifocal sunglasses also have easily-adjustable nose pads which allow for individualized fitting. To aid the designed durability, each pair of Dual Eyewear glasses comes in a nice cloth pouch inside a protective case.

With competitive pricing, a lifetime warranty and a 30-day satisfaction guarantee, Dual Eyewear provides a quality product that every bifocal-using pilot should consider.  

John “Omar” Bradley lives in Chattanooga and now flies for a major airline after a 23-year Air Force and Air National Guard career flying the T-37, T-38, B-1, T-1, KC-135 and LC-130. As an ATP, CFI-I, CFI-G and SES-rated pilot, he currently has over 6,600 hours in various military and civilian aircraft, including more than 1,500 hours in single-engine aircraft. Send questions or comments to


NPRM FAA-2017-1059 – Checking for Main Wing Spar Corrosion in Cherokees 

NPRM FAA-2017-1059 – Checking for Main Wing Spar Corrosion in Cherokees 


Over 10,000 Piper PA-28 and PA-32 series aircraft will be affected by a proposed Airworthiness Directive requiring inspection of the main wing spar for corrosion. Associate editor SCOTT KINNEY decides to act now to inspect his Cherokee and secure his peace of mind.


One of the benefits of hanging around type-specific flying forums on the internet is that you’ll often get wind of FAA Airworthiness Directives (ADs) before they’re made public. I’d chanced across just such a post on Nov. 6, 2017.

The poster claimed that Piper Service Bulletin (SB) No. 1304 was about to become an AD, affecting thousands of aircraft. SB 1304 mandates a “thorough one-time inspection of the wing root area for corrosion” and lays out steps to be taken if corrosion is found. To perform the inspection, an access panel must be installed in each wing if one does not already exist.

Sure enough, the next morning, my email inbox contained a confirmation of the rumor: the FAA was moving to adopt SB 1304 as an AD after a 45-day comment period. (See page 60 of this issue. —Ed.) The Notice of Proposed Rulemaking (NPRM) states that compliance will be required within the next 100 hours or 12 months’ time in service from the date of the AD.

Summary: 11,476 PA-28 aircraft owners will soon be getting potentially expensive news.

I’m one of them.

My 1963 Piper PA-28-180 Cherokee 180, N7294W, has served me well for the past few years. As with many older birds, she has a few negatives in the logs. Four Whiskey lived her first several years near the beach in Southern California. I’d guess she was parked outside too, as the logbooks show a few corrosion repairs in the mid-1970s. Since then, she’s been primarily a high desert airplane.

Why not wait?

I decided to move forward with the inspection right away. I suppose I could’ve held off until my July annual and/or until the AD wording was finalized. It may be that the final AD has other accepted methods for inspection (borescope?) that don’t require cutting large access panels in the lower wing skins.

However, I had never seen the spars on N7294W with my own eyes. I am not sure I would’ve been happy flying the airplane for many more hours knowing the potential consequences of wing spar corrosion. November is also a good time of year to get work done on an aircraft in Oregon—it’s not flying season.

And I kept coming back to the reasons behind the proposed AD. A failed main spar means that your wings may fall off. In my book, that’s a very bad day.

Checking for access panels

The first step was to check for existing access panels. I thought that perhaps the panels could have been installed as part of some of the previous repair work. Since I was at home and had the aircraft logs on hand, I checked for any mention of SB 1304, SB 1244B or SB 789A (the latter two Service Bulletins also recommend addition of the access panel kit). Nothing.

The previous owner did pull the fuel tanks about seven years ago to check for spar corrosion (Piper SB 1006), but that’s further outboard on the wing. I went to the airport and crawled under the wing. Maybe the work hadn’t been logged and the panels were already in place.

No joy. I fired up Google and went parts shopping.

Finding parts

The NPRM estimates the cost of Piper’s 765-106V kit “that contains provisions to install inspections access panels on both wings” at $175. I lucked out and found a new old stock kit for a little less than that.

Since the announcement on Nov. 7, 2017, these kits have gotten increasingly difficult to find. Many vendors sold out of 765-106V in the first two days after the announcement, though they have since restocked.

Current street price for P/N 765-106V is between $200 and $250; slightly higher than the $175 estimated in the NPRM. As of early December 2017, PFA supporter AirWard shows a dozen kits in stock at a price of $229; a Google search for “Piper 765-106V” will give the most current situation. I would expect these kits to become increasingly rare or backordered immediately after the final AD is announced.

Installing the access panels

I contacted PFA member Tony Hann at Infinite Air Center in Albany, Oregon to schedule the work. Tony and his lead A&P/IA, Robert Lind, operate several PA-28s out of Albany Municipal Airport (S12). Robert has been working with Piper aircraft for more than 30 years and their shop is just a short hop from my home base.

Once I had my parts in hand, I braved the stormy mid-November weather and flew Four Whiskey up to Albany in what I’ll generously call “imperfect VFR conditions.”

Nuts ‘n bolts

Robert, Tony and I unpacked the kit’s contents onto the wing of the aircraft.

They’d ordered a few kits from Aviall to service their PA-28s. We compared the Aviall kits with my kit from Piper. My kit—dated 1987—matched up parts-wise, meaning Piper hasn’t changed the kit contents in 30 years.

The kit consists of two reinforcing doubler plates and two inspection covers. There are also 40 AN426AD4-4 rivets, used to affix the plates to the lower wing skin and 16 MS24693-S48 machine screws for attachment of the inspection covers to the doubler plates.

The Piper instructions are skimpy, to say the least, and leave some room for imagination (or improvisation?):

1. Skin cutout to be located midway between ribs and midway between the main spar and stringer as shown in
Figure 1 (Sheet 4).

2. Locate and install doubler 38571-02 as shown and attach to skin using [P/N] 420 722 rivets. Dimple for C/S rivets.

3. Cover 38572-02 can be installed/removed as required, using [P/N] 414 761 fasteners.

Other vendors have been kind enough to include more detailed instructions and a tool list. I’ve seen the documentation AirWard supplies with its kit, and it’s a very helpful supplement.

Positioning the inspection panels

The Piper instructions that came with my kit, those in the new Aviall kits and the drawings in SB 1304 all specify slightly different placements of the access panel in relation to the main spar, ribs and stringers.

After some deliberation over the instructions, Robert, Tony and I positioned the cover and used it as a template to define the cutout area.

We marked the hole as specified in the new Piper instructions and SB 1304—approximately 2 inches aft of the main spar rivet line and 3 inches outboard of the rib at WS 24.240. The long and short of it is that you want to leave sufficient space on every side of the access hole to be able to rivet the doubler in place without getting too close to the spar or ribs.

It’s also important to understand that this is a recessed access plate; it’s different from those further out on the wing. Those are attached to the outside of the lower wing skin. When finished, the new inboard inspection cover will be flush with the wing skin.

Cutting access holes

Out came the power tools. I closed my eyes and turned the other way as Robert began the surgery. He drilled a 1-inch pilot hole with a step drill to provide a starting point.

For the primary cut in the skin, Robert chose a Dremel-like rotary tool with a fine tungsten carbide cutting bit. Smart choice. It allowed him to make a smooth radius cut in the thin aluminum skin.

It was helpful to have two sets of hands to finish the cuts—Robert on the Dremel and me holding the cutout piece in place to ensure it wouldn’t prematurely depart the wing. Wear eye/face protection and appropriate clothing when working with the Dremel as the hot aluminum shards fall straight down.

I cleaned up the edges with a half-round file while Robert moved on to the other wing and repeated the process. I held off from peeking inside until we were done cutting the panels.

The inspection

With the holes cut, it was time for the moment of truth. Robert asked, “Do you want to do the honors?” I meekly replied, “Uhh, I guess.” If the spars showed significant corrosion, it likely meant a repair bill of several thousand dollars.

I grabbed a flashlight and inspection mirror and rolled back under the right wing on a mechanic’s creeper. I poked the mirror up into the hole.

Oh, thank God. My wings will not fall off.

The main spar looked pristine. The aft spar was excellent as well. The WS 24.240 (inboard of the access panel) and 36.920 rib (outboard of the panel) showed some oxidation and very minor surface corrosion. Four Whiskey’s main spars had been treated with chromate at the factory, but the ribs hadn’t, so the corrosion on the ribs was no surprise.

Robert took a look and confirmed my initial thoughts. “That’s real clean. Great news!” The left wing looked the same.

It wasn’t all sunshine and rainbows, though. The inspection panel in the right wing allowed me to see the underside of the wing walk skin. A few minor cracks had developed in the reinforcing louvers—a common problem with PA-28s. I have felt a slight bit of oil-canning in the wing walk in the past, so I wasn’t shocked by the finding. Such is life with an old aircraft; one more thing to fix.

Cleaning and priming

Robert and I cleaned the interior of the inspection area with a degreaser spray per Part I, Step 3 of SB 1304. After 50 years, the wings had an impressive collection of dead bugs and grime. We reinspected the spar after cleaning and found no corrosion.

SB 1304 states that if corrosion is found in the main spar area, it must first be removed per FAA Advisory Circular AC 43.13-1B, Chapter 6. The affected areas then must be measured for minimum thickness. It is not possible to directly measure all dimensions, so nondestructive methods (ultrasound, eddy current, etc.) may need to be used.

If the thickness of the parts is greater than the limits specified in SB 1304 Part I, Step 5, the areas can be epoxy primed and the aircraft returned to service. The SB contains a list of approved epoxy primers.

If the thickness is below minimums, an FAA-approved structural repair must be performed. This is likely to be an expensive proposition.

We chose to clean and apply epoxy primer to the ribs to ensure no further corrosion on these surfaces. Though this action is not required by SB 1304, it made sense to do with the aircraft already opened up.

Affixing doublers and buttoning up

After the inspection and corrosion mediation steps were complete, Robert went to work on affixing the doublers. Riveting isn’t my strong suit, so I played the role of gofer.

Each doubler plate required 20 countersunk rivets. The rivets are equally spaced around the doubler plate, approximately 5/16 of an inch outside the cutout. Robert used a drawing compass, a slide rule and some mechanic’s magic to get the spacing right. The AirWard instructions contain an error here. They give a layout scheme for 24 rivets per plate, not the 20 per plate that is specified in the Piper documents. They are otherwise really helpful.

Drilling the holes for the rivets is a six-step process. First, Robert clamped the doubler in place. Next, he drilled 1/16-inch holes through the skin and doubler. He then enlarged the holes to 1/8 inch.

Once the holes were drilled, he removed the doubler and deburred the holes. The fifth step was to dimple the holes with a rivet squeezer and appropriate die. Finally, he used Clecos to hold everything in place while he set the rivets into the skin and doubler with the squeezer. The right tools made this job go quickly.

When he finished riveting, Robert made an entry in the logs noting compliance with SB 1304. All that was left was to install each cover with the eight machine screws. I managed this on my own. Four Whiskey needs a bit of paint touch-up in other spots, so I plan to paint the covers and rivet heads later on this winter as a part of that project.

Final thoughts

It took about eight hours of work for Robert to install the panels, clean the interior of the wing and perform the inspection. The NPRM estimates six hours’ labor for the panel installation and two hours for the inspection. For obvious reasons, the NPRM does not estimate labor time or parts costs for corrective actions, as these may range from a small area of sanding/priming all the way up to spar replacement. Nor does it account for cosmetics. Paint touch-up may take additional time.

I’d encourage those owners whose aircraft are affected to consider complying sooner rather than later. It may be that your aircraft already has the access panels, in which case it’s a quick inspection. Even if your aircraft doesn’t have the panels, the installation and subsequent inspection is time-consuming, but isn’t particularly complicated.

Installation of the panels can facilitate later inspections required by this or other ADs or SBs. Additionally, you’ll have better access to the inboard areas of the wing for future upgrades (pulling wires) or repairs (the wing walk comes to mind).

Now that I’ve seen the clean spar with my own eyes, I’m 100 percent confident that I have structurally sound wings holding me up in the air. It’s hard to put a price on that feeling of security.

Scott Kinney is a self-described aviation geek (#avgeek), private pilot and instructor (CFI-Sport, AGI). He is associate editor for Piper Flyer. Scott and his partner Julia are based in Eugene, Oregon. They are often found buzzing around the West in their Cherokee 180. Send questions or comments to .



Infinite Air Center



Piper Service Bulletin No. 1304
“Main Wing Spar Inspection,”
published Aug. 23, 2017


Piper Service Bulletin No. 1244B

“Aft Wing Attach Fitting Inspection Requirements,” published Oct. 29, 2015



Piper Service Bulletin No. 789A

“Aft Inboard Wing Access Panel Retrofit and Aft Wing Spar Modification”

published May 7, 1985

Notice of Proposed Rulemaking (NPRM)

Docket No. FAA-2017-1059; Product Identifier 2017-CE-035-AD

https://www.federalregister.gov/documents/2017/11/07/2017-24083/airworthiness-directives-piper-aircraft-inc-airplanes (See page 60 of this issue. Comments closed Dec. 22, 2017. —Ed)

P/N 765-106V – VENDORS

AirWard, Inc.
– PFA supporter






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