Failure to Use Carb Heat Brings Down Piper

I confess I've been a little cavalier about applying carb heat in my Cherokee because they're not particularly susceptible to icing, right? Here's a cautionary reminder.

Failure to use carb heat brings down Piper
Posted by Meg Godlewski · December 20, 2010
Link to Story

Aircraft: Piper Cherokee. Injuries: 3 Serious. Location: Kapolei, Hawaii. Aircraft damage: Substantial.

What reportedly happened: The airplane was level at 1,500 feet MSL when the flight instructor had the private pilot receiving instruction reduce power and glide towards the runway for a touch-and-go. The CFI said they did not use carburetor heat nor did they clear the engine during the glide. The pilot landed the plane, then advanced the throttle for takeoff. Immediately after liftoff, the flight instructor noted that the engine was not producing full power. He took control of the airplane, checked the engine instruments, fuel tank selector position, and fuel pressure, and confirmed that the throttle and mixture controls were full forward. The CFI did not apply carburetor heat. The airplane did not have enough power to reach an altitude that would allow it to avoid obstacles at the end of the runway. The Piper collided with trees and a power line.

During the post-accident examination no airframe or engine pre-impact mechanical discrepancies that would have prevented normal operation were found. The fuel tank selector valve was found slightly out of the detent for the right tank position, but it still offered about 80% of the normal opening for fuel to pass. According to the engine manufacturer, carburetor ice can form under a relative humidity of 50% to 60% with any outside air temperature from 20° to 90° Fahrenheit. The calculated relative humidity at the time of the accident was 79%. A carburetor icing probability chart indicated that the conditions were in the range for serious icing at glide power. Investigators determined that the partial loss of engine power was likely a result of the formation of carburetor ice.

Probable cause: The partial loss of engine power during the initial climb due to the failure of both pilots to use carburetor heat during a long descent for landing in carburetor icing conditions and the flight instructor’s inadequate supervision of the flight.


  • Forty years ago when I lived on Oahu, I flew with the Air Force Aero Club at Wheeler AFB. Can't remember ever using carb heat during that 14 months.
  • I use it all the time as it only robs about 100-150 RPM and cheap insurance I think to prevent icing on the Piper, even though Pipers are less likely to have carb ice as compared to Cessnas why not turn it on when entering the pattern as an extra precaution.
  • What does the Cherokee POH say about carb heat?
  • Yeah, that's about what mine says too.
  • Excerpts from the 180C POH. The guidance is pretty explicit:

    Cruising: "The continuous use of carburetor heat during cruising flight decreases engine efficiency. Unless icing conditions in the carburetor are severe do not cruise with the heat on. Apply full carburetor heat slowly and only for a few seconds at intervals determined by icing severity." [Me: And land as soon as possible!]

    Landing: "Carburetor heat should not be applied unless there is an indication of carburetor icing, since the use of carburetor heat causes a reduction in power which may be critical in case of a go-around. Full throttle operation with heat on is likely to cause detonation."
  • It's my understanding that the Cessna POH technique is different from the Cherokee POH technique.
  • I was always taught to apply it during your pre landing checklist, and when we did a touch and go it was just automatic to push the carb heat in at the time you apply full power again. Takes an extra .5 second. I got my training in a C-152.
  • Piper Tech,

    Great procedure for Cessnas, not so much for Piper Cherokees. I understand that the location of the carburetor has a lot to do with whether icing frequently forms, and on my Cherokee, the carburetor appears to be mounted below the oil sump, where it undoubtedly receives enough heat to prevent most icing problems. The situation in Hawaii is obviously different than in most places on the mainland due to very high humidity. I've had carb icing in a Cessna during cruise (as a student pilot on a solo cross country) on a very nice summer day. Proper application of carb heat solved that problem. I check carb heat on the Cherokee during run-up, but could count the number of times I applied carb heat in flight on one hand in 9 years. It would certainly be a good idea to check or apply carb heat if the humidity is 80 percent or more, even in a Cherokee.
  • good Morning, I did all my flight training in injected as well as carburated C-172's. My checkout in the carburated 172 was, "power back carb heat on" always. I fly my 140 the same way and as was written previously a few times during cruise. I have a carb temp gauge and here in the mid-atlantic states I have seen carb temps at zero during cruise. No brainer for me, it's so easy, and if checklists are used properly, it will be off for landing and takeoff. And since the gauge is on my wife's side of the panel she points it out to me, as well as alot of other stuff!
  • Yes, and if you go by the Cherokee POH, you will not normally use carb heat. I make no recommendation either way.
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