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Smooth, Simple, Stable: Piper's Archer DX

Smooth, Simple, Stable: Piper's Archer DX

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According to Boeing’s Pilot and Technician Outlook (2015–2034), the world’s airlines will need to recruit and train some 558,000 new pilots over the next 20 years—with the vast majority needed in the Asia Pacific region. 

The challenge for the training-aircraft manufacturing industry, heavily based in the United States, is developing an airplane that will provide the level of advanced system familiarity that these students will need and powering it with an engine that doesn’t rely on hard-to-get 100LL Avgas. For a U.S. aircraft manufacturer, it seems like right now is a great time to introduce just this type of training aircraft to the global market.

A global training market 

“From Piper’s perspective, the fact that the trainer market is becoming more active with respect to large fleet purchases prompted us to actively develop a new training aircraft that had a powerplant that is relevant worldwide,” explained Piper’s director of marketing and communications Jacqueline Carlon. 

“Diesel aircraft engines are far more cost effective outside of the U.S., and keeping in mind that we are selling a lot of aircraft into Asia and throughout the Pacific Rim region, this engine type became our obvious choice.”

“Our solution was to partner with Continental Motors to develop a firewall-forward diesel package using its 155 hp turbodiesel CD-155 engine on the Piper Archer,” Carlon said. “We felt this engine gave us the best combination of power, reliability and efficiency.”

As you probably recall, long before Continental bought the rights to the Thielert/Centurion diesel engine technology, the original company had earned an STC to retrofit the then-Thielert 135 hp diesel onto the Piper PA-28-161 Warrior. 

Since the STC already existed, why not just offer the new CD-155 on the Warrior, which is already a market-leading training platform? 

“The primary reason that we focused on the Archer for the diesel engine offering was the fact that we did not certify the Garmin G1000 in the Warrior. It has the G500 displays,” Carlon explained. 

“The majority of large providers require the G1000 package for advanced training. That kind of made the decision easy.”

Creating the DX

As you would expect, there’s a bit more needed to create the DX than just sticking a Continental CD-155 on the Archer’s nose. Because of past experience with the PA-28-161 STC, Piper’s learning curve was shortened, but not eliminated. 

One of the most challenging parts of the project was getting a fully-equipped Archer LX (S/N 701) over to the Technify Motors’ facility in Sankt [St.] Egidien, Germany. That’s a long trip for a little airplane—and while it’s become common practice, navigating several winter storms along the route made this trip a bit more challenging.

Once S/N 701 arrived, the Technify team was ready to get rolling. Markus Steinberg, head of quality and certification at Technify Motors GmbH [Continental Motors] explained that while the company could use some of the data from the earlier Warrior STC, the Archer DX project required some fresh thinking. 

He said that one of the biggest changes was the modification of the Archer’s engine mount and nosegear.

“The devil is always in the details,” said Steinberg. “We could not use the standard engine mount because the angle of the [Archer’s] nosewheel is slightly different and we didn’t want to risk any nosewheel shimmy due to the heavier engine. So we had to copy the angle of the nosewheel on the Warrior and integrate that into a new design for the Archer.

“Of course, since this is a common rail injection diesel engine, we had to modify the factory fuel system with new return lines while ensuring that all the materials and components were capable of dealing with jet fuel,” he continued. 

“We also had to install a second ship’s battery behind the rear seats for the FADEC. That was a major upgrade.”

All totaled, Steinberg said that the DX transformation necessitated 13 changes to the existing PA-28 STC. Among the bigger changes are a new three-blade MT composite propeller and spinner, reworked electrical and fuel systems, and a new cowl design incorporating an integrated air scoop for heater cooling.

“I think the most challenging of them all was the integration of the new G1000 software,” Steinberg explained. “That was new to Garmin as well. This new software version is different from [what is] flying on other aircraft, so we had a lot to learn.”

Steinberg and his team are rightfully proud of the fact that even with 701 arriving a bit late, they were still able to celebrate its first flight with the Continental CD-155 diesel engine on Christmas Eve 2014.

“Timing was a major issue. We had to have the EASA STC issued by April in time for the aircraft’s introduction during the 2015 Aero Friedrichshafen airshow,” he said. “One thing you learn about schedules is after the day comes the night—so if you’re not done, you just keep working into the night.”

Time to fly

Recently I had the opportunity to fly the DX and put it through its paces. I’m figuring pretty much everybody reading this magazine has flown a member of the venerable Piper PA-28 family at least once so I’m going to concentrate on what’s different about the Archer DX. 

Walking up to the airplane, the first thing you notice is the propeller. The three-blade MT propeller really gives the Archer DX a shot in the arm from a styling perspective. 

Before saddling up, Piper’s Chief Pilot Bart Jones walked me through the preflight. Again, it’s pretty much the same as with any Archer. The only real difference is when you first flip on the master power, you need to give the battery indicator on the G1000 a look just to make sure you have plenty of juice in the battery to crank the diesel over. Starts with ground power are prohibited. 

Next, take a minute to look up in the front of the cowling. There’s a little door you open to check a sight glass that shows the gearbox oil level. Speaking of oil, the Continental diesel uses AeroShell Diesel 10W-40, which is not typically found at FBOs. It’s a good idea to carry a quart or two with you. 

The only other difference is when you drain the sumps, you need to make sure the fuel is the color of weak tea and not the blue of 100LL. Piper has placed large “Jet A-1” stickers and used heavy-duty stainless steel fuel filler caps on the DX, but you need to be wary of misfueling the Archer. (If it were my DX, I’d want to supervise every refueling.)

Climbing in the left seat and strapping in is all typical Archer. As you would expect from the top-of-the-line model, the DX’s interior is very nice especially for an airplane aimed at the training market.

Push to start

As you’ve no doubt read somewhere, the diesel engine is literally push-button easy to start. Set the brakes, ensure the thrust lever is set to idle (you have to love having a “thrust lever” in an Archer), flip on the ship’s power, wait for the glow control light to go out, reach up to the overhead switch panel and press and hold the starter button until the engine starts. 

But pay close attention. If you have your headset on, you won’t actually hear the engine start; it becomes obvious when the prop starts spinning. The entire procedure is done in less time than it took you to read this.

Next comes a FADEC Backup Battery Test—a procedure that includes a test of the emergency battery. As I mentioned earlier, the battery’s health is extremely important in the Archer DX. Since the FADEC runs the airplane, and the aircraft’s electrical system runs the FADEC, you need to make sure the alternator is charging the battery before you leave the chocks. 

You do have a second ship’s battery (and the FADEC has a backup battery of its own), but it’s only good for 30 minutes of flight. An alternator failure in an Archer DX is a “land as soon as you can” occurrence.

While these tests are being done, you’re giving the engine oil and coolant time to reach operating temperatures. Once the temps are in the green you can taxi to the runup area and perform the pre-takeoff steps including the mandatory FADEC and Propeller Adjustment Function Check. 

Speaking of taxiing, the first thing that’s obvious when you advance the thrust lever to taxi is how incredibly quiet and vibration-free the diesel engine is. It’s turbine-like in its feel and operation—another benefit when you’re talking new-generation trainer. 

Once we reached the runup area, Jones walked me through the routine. Everything is pretty much like you’d expect but when it comes time to run up the engine, instead of pushing this and cycling that, you just set the power to idle and press and hold the FADEC Test button. The dual channel computers do the rest while you monitor the G1000 displays. 

The last check is to push the thrust lever up to the stops and hold it for a count of 10. You need to see at least 94 percent power with the tach between 2,240 to 2,300 rpm. Max rpm is the same in the diesel Archer as you’ll find in the Avgas model.

Up, up and away

One last thing before calling Vero Beach Tower for takeoff is to set the flaps to 25 degrees. Since I can’t recall ever using flaps for a normal takeoff in any Archer, this step got my attention. 

“That’s the standard takeoff setting for the DX,” Jones explained. “Because this is a 155 hp engine, the 25 degrees of flaps give you the same takeoff performance as the 180 hp Archer.”

Jones and I checked, and according to the POH, the standard Archer would need 1,700 feet of runway to clear the proverbial 50-foot obstacle on a standard day. The 155 hp DX would need 1,673 feet of concrete with 25 degrees of flaps. 

Cleared for takeoff, I advanced the thrust lever to the stops and just flew her off like any Archer. And that’s pretty much how the DX felt for the 1.5 hours Jones and I spent carving up the sky above Vero Beach: an Archer is an Archer is an Archer.

Thanks to the constant speed propeller, you’d really never know you are giving up 25 hp to the Avgas version. The climb numbers for both aircraft are within three fpm of each other—with the DX taking the lead. Jones attributes this to the FADEC and constant speed propeller. 

You can’t talk diesel without mentioning fuel economy, and Jones pointed out that you really don’t see big advantages until you get up higher. Doing touch-and-goes is pretty much a wash.

On this flight we leveled off at 5,500 feet, where I set the power at 70 percent. Once everything was stabilized, the G1000 indicated 101 knots with a TAS of 112 knots. 

Fuel flow was just under six gph, so a full load of 48 gallons of Jet-A would give us an endurance of eight hours. Of course, your mileage may vary.

Jones said that had we climbed even higher, we would have seen both higher speeds and lower fuel burn, offering operators a much more efficient engine/airframe package. 

“The turbocharger and FADEC takes all the guesswork out of engine management in the DX,” Jones said. “You are getting the optimum performance and efficiency at every altitude and you don’t have to be guessing if you’ve got the mixture right. The computer takes care of it all.”

Aside from the FADEC and, as I mentioned earlier, the amazingly quiet cabin—while we were cruising along, Jones and I were able to remove our headsets and hold a regular conversation (try that in a standard Archer)—the DX handles like any Piper PA-28. Smooth. Simple. Stable. Reliable. Everything I’d want in a training airplane. 

Yes, the Archer DX does cost more than the standard model, and yes, the Continental CD-155 does have a 1,200-hour TBR (Time Between Removal)—which the company is working diligently to raise—but even with those points, the diesel powered Archer DX will make a really great training platform.

A better learning environment

As Carlon pointed out, along with the global fuel flexibility of the diesel, the quiet operation and smoothness of the cabin will provide an exceptionally comfortable setting. 

“It’s a much better learning environment for basic and advanced students,” she said. “It’s quieter with less vibration, which means students and instructors will feel less fatigued after hours in the cockpit. Less fatigue means better learning.”

Even after only 1.5 hours in the left seat, I couldn’t agree more.


Dale Smith has been an aviation journalist for 30 years. When he’s not writing aviation articles, Smith does commission aircraft illustrations specializing in seaplanes and flying boats. Smith has been a licensed pilot since 1974 and has flown 35 different types of General Aviation, business and World War II vintage aircraft. Send questions or comments to .



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