July 2013-
Q: Hi Steve,
I am a member of a flying club and a Sunday flyer. One thing our club does on a monthly basis is fly-outs. We usually get 15 to 20 club members (it’s a big club) together and share flying duties.
Last weekend we flew into Columbia Airport (O22) in the California foothills for Sunday brunch in historic Columbia, which is only a short walk from the airport.
Anyway, while I was there I heard guy saying to another that his Comanche doesn’t have a stall warning system. How is that possible? I thought every airplane had to have one.
—Club Flyer
A: Hi Club,
You’re not the only one who has made that same assumption. But it’s not true. Most of the small single and light twin airplanes still flying today were certified under a set of rules commonly called “CAR 3.” CAR is an acronym for Civil Air Regulations.
This 104-page document defined the requirements for building and equipping airplanes when it was adopted in 1949. It was updated in 1956. Regulation 3 is titled “Airplane Airworthiness – Normal, Utility, and Acrobatic Categories.”
The majority of today’s single and light twin airplanes are CAR 3 airplanes. One category in CAR 3 is miscellaneous equipment; it does not require the installation of a stall warning device or system.
The newer certification rules address stall warning indicators. Federal Aviation Regulation (FAR) 23.207 does mandate the installation of a stall warning system. Here’s a portion of that regulation:
(a) There must be a clear and distinctive stall warning, with the flaps and landing gear in any normal position, in straight and turning flight.
(b) The stall warning may be furnished either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight.
The regulations don’t specifically require that little vane/switch that’s installed in the leading edge of the left wing of almost every GA airplane.
I do know that the Piper Comanche series of airplanes does have a listing in the airplane Type Certificate Data Sheet (TCDS) under miscellaneous equipment for “Stall Warning indicator installation.” The vane/switch (part number 450 726) is required equipment in the PA-24-250, the PA-24-260 and the PA-24-400, but not for the PA-24, which has the 180 hp engine.
My PA-24 does not have a stall warning device although there is a cutout in the left wing skin to install one.
My PA-24 does have an aerodynamic stall indicating device in the form of a strip that’s riveted to the leading edge of each wing. This strip is located so that it upsets a small portion of the smooth airflow over the wing as the wing approaches stalling speed. That burbling air flows aft and hits the outer end of the stabilator. (At least, that’s the way it was explained to me.)
Apparently Piper was able to certify the PA-24 using the aerodynamic warning device but either wasn’t able to on the others, or chose to go with the more common stall vane/switch configuration.
The CARs and the FARs do provide some latitude for compliance with certain rules for aircraft manufacturers. The stall warning rule is an example of this.
Happy flying.
Q: Dear Steve,
I am flying a Piper Arrow III and have recently discovered that my stall warning horn doesn’t make any sound when I pushed the little tab up during my preflight walkarounds.
I never hear this thing go off during my normal flying, but I heard it plenty while my instructor was prepping me for my commercial pilot checkride.
When I mentioned this to my flying buddy he said something like, “Too bad, those things are expensive.”
Are they really that expensive, and if so, where’s the best place to get one?
—No-Horn Harry
A: Dear Harry,
Congratulations on going for your commercial pilot rating. It’s always a good idea to keep tuning up your skills.
Your flying buddy is half right. A new vane/switch—part number 450 742 for your airplane—is expensive, but the bill is not nearly as expensive as it once was.
To the best of my knowledge Safe Flight Instrument Corp. of White Plains, N.Y. was the sole supplier of stall vane/switches for decades. The product was well built and rarely failed, but could be expensive. As I recall from my years in a Cessna shop, the price for a new unit used to be more than $2,000.
Today you have other options. One is to attempt to clean your existing switch. Some shops have been able to successfully clean the vane/switches by briefly submerging the switch in the cleaning solution in an ultrasonic cleaner—if the only problem is dirt and crud on the contacts.
The second option is to locate a used, serviceable unit. I typed the part number into my favorite search engine and at least 30 references popped up. Most were from salvage yards. A used part can be installed if your mechanic is willing to attest to the part’s airworthiness. Some mechanics are no longer willing to install used parts. (If you go this route, use PFA’s parts locating service to save time and money. You can call us at 1-800-493-7450, or fill out the request form at www.piperflyer.com. —Ed.)
The last option is to buy a new vane/switch. Fortunately, the company that is fast becoming the go-to parts warehouse for GA aircraft—McFarlane Aviation in Baldwin City, Kan.—offers new FAA approved replacement vane/switches for a wide range of GA airplanes, including your Arrow III. List price is $595.
One of these options will get you back in the air.
Happy flying.
Know your FAR/AIM and check with your mechanic before starting any work.
Steve Ells has been an A&P/IA for 39 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 editor@www.piperflyer.com.
RESOURCES >>>>>
Historical Civil Air Regulations and Current FARs
https://www.faa.gov/regulations_policies/faa_regulations/
McFarlane Aviation
mcfarlane-aviation.com
