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Q&A: Emergency landing gear extension, troubleshooting water in the fuel and checking the idle mixture

Q&A: Emergency landing gear extension, troubleshooting water in the fuel and checking the idle mixture

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May 2015-
Q: Hi Steve,
I watched a gear-up landing at my local airport a week ago. Nobody in the Piper Arrow was hurt, so it was a good landing. But after all the facts were known, it appears as if the cause was the pilot didn’t know how to, or got emotionally seized up, when he attempted to do an emergency gear extension.

As I pondered this I wondered if I would be able to get the gear down in my Arrow II if something went wrong. I’ve read the book on the emergency gear-down procedure, but I’ve never actually done it.
I decided to survey the other pilots here that fly retractable landing gear airplanes and found that only one or two out of 14 had ever completed an emergency gear-down procedure while flying.

I know I can re-read through the manual, and sit in the cockpit and coach myself through the steps when I’m on the ground. I believe I understand the landing gear system, but wonder if I should insist that my instructor let me perform an actual emergency gear extension.
What do you think?

—Landing Gear Gary

A: Dear Gary,
I’m impressed with the fact you’re striving to learn all you can about the landing gear system in your Arrow II. An intimate knowledge of systems increases confidence and makes flying safer.

The landing gear (LG) system in your PA-28R-200 is pretty simple. During the gear-up cycle, the LG is retracted using hydraulic pressure generated by a pump/reservoir/valve assembly located aft of the baggage compartment on the pilot’s side of the centerline.

Once the gear is up and the actuating cylinders have reached the limit of up travel, the hydraulic pressure builds to approximately 1,400 psi. At that point a pressure sensing switch turns off the pump. A one-way check valve seals the up pressure line and the LG legs are held up by the captured hydraulic fluid.

If there’s a small leak past the check valve or past a piston in one of the actuators, pressure will bleed off. At approximately 1,100 psi the pressure sensing switch will turn the pump motor back on until the pressure again builds to approximately 1,400 psi.
An emergency landing gear extension is quite simple: pushing the emergency gear extension lever on the pilot’s side of the console between the front seats opens up the gear-up fluid lines.
Without pressure, the gear will fall out of the gear wells and lock itself down. Built-in restrictions, called snubbers, in the fluid lines prevent the LG from slamming down into position. Extension of the nosegear is assisted by springs.

As you know, there is an in-flight emergency gear-down test procedure in the service manual of your Arrow. Get together with your flight instructor, review the procedures and then go out and practice.
Gaining this kind of experience with the steps involved in extending the LG in an emergency will go a long way in easing your concerns.

Happy flying.

Q: Hi Steve,
Our 1967 Arrow will experience very rough—but quite intermittent—engine operation in very cold weather. I’ve noticed this hiccup occurs shortly after departure and also on taxiing after landing. The coughing eventually stops, but it is somewhat unnerving, especially on departure.

The engine-driven fuel pump was replaced in 2014 and seemed to resolve the problem. However, the quirkiness reared its ugly head again last winter. The airplane is kept in a heated hangar, and temperatures during flight are ranging from 20 degrees to -20 degrees F.
Speculation suggests that frost on plugs and/or injectors turns to water and gets ingested into the fuel, or a possible air intake blockage.

Additional information:
1) The phenomenon only occurs in cold weather, and did not occur before we had a heated hangar.
2) The coughing primarily occurs when the Arrow is in a nose-up pitch attitude. Is a vent getting blocked?
3) There is a delay of at least 30 to 60 minutes after leaving the hangar before it happens. Evidently the issue is dependent on outside temperature? When it occurred for the first time last winter, it took about 45 minutes and we were departing Duluth, Minn. (KDLH), nose up.
Perhaps water is condensing because of temperature decrease from hangar to outside, somewhere in the fuel system—probably on the right side—and then freezing, creating ice crystals and causing a partial restriction of fuel flow?
Any suggestions would be most welcome!

—Arrow Angst

A: Dear Arrow,
It sounds like you’re getting little bits of water in the fuel. Not enough to cause a real emergency or loss of power, but enough to cause a tighter grip on the yoke.
The most common causes are a leaky fuel cap or condensation. Since you’re moving your airplane from a heated hangar I’d bet that your problems are condensation-based.

Try to shake the wings by putting one hand on top of the wing and one hand on the bottom of the wing at the wing spar, and do your best to move the wing up and down. The idea is to dislodge any water globules and get them flowing to the fuel sump drain.
Then drain a lot of fuel—at least a quart—out of the right tank. (Might as well do the left tank, too, since you’ll be warmed up!) Keep draining until you no longer see any evidence of water.

The next thing to do is add isopropyl alcohol to the fuel tank. The alcohol absorbs water and prevents water in the fuel from freezing. Don’t use rubbing alcohol even though it does contain isopropyl alcohol; it’s diluted.
I’ve included a fuel additive chart for you to refer to (page 23). One example adds five cups of alcohol to 30 gallons of fuel. If you’re having a hard time rounding up isopropyl alcohol, you can order Prist Hi-Flash Lo-Flo anti-icing fuel additive from Aircraft Spruce and Specialty.

After pondering your write-up, it appears that in addition to the water from condensation you have an idle mixture problem. It’s important to reset the idle mixture and idle speed with seasonal changes. If that wasn’t done it may explain the spark plug fouling and hard starting problems.
A simple test to determine if the idle mixture is set correctly is to slowly pull the mixture control knob aft at idle rpm after a flight. (It’s important that the engine is at operating temperature for this test.) Some maintenance texts suggest doing this test at 600 rpm; some at 1,000 rpm.

A properly set idle mixture will cause a slight (25 to 50 rpm) rise prior to engine cutoff. If you have an analog tachometer it may not show this slight change, but you’ll be able to hear the rise if it’s there.
If the increase is greater than 50 rpm, the mixture is set too rich; if there’s no rise, the mixture is too lean.
Please let me know if these tips work.

Happy flying.

Know your FAR/AIM and check with your mechanic before starting any work.

Steve Ells has been an A&P/IA for 43 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as associate editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Paso Robles, Calif. with his wife Audrey. Send questions and
comments to .

RESOURCES >>>>>

Prist Hi-Flash Lo-Flo
Anti-Icing Fuel Additive
aircraftspruce.com


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