PARTIAL POWER LOSS DOES HAPPEN ....

Acknowledgements: Mastery Flight Training Inc. (Thomas P. Turner & Steve T}

(Ed. Note: A very good dialogue recounted by Tom concerning a student’s actual experiences during an early stage in his training)

Student Steve T said: “I had my first emergency off field landing in my third lesson: power failure on take-off. The previous week, a soloing student pilot had noted a loss of power during the landing stage…. the engine was examined …… [despite the fine weather conditions]  the issue was attributed by the A&P mechanic to the carb de-icing heat not being on, …... the plane was returned to service, and my CFI used it for three hours before we started our lesson. Everything checked out normally before flight …. I took off at nominal 2700 RPM …. I had asked to feel the effects of flap at take-off, so we'd added the first notch …. meaning we were higher and safer than with flaps up.

We got to around 600 feet….when revs dropped back to 2000 RPM …. my CFI told me to pitch down, and I initiated a gentle bank to the left while he tried to manipulate the controls to get more RPM. Nothing helped …. we were well beyond glide to the airport, and too low to attempt to fly on to a nearby airport …. we immediately entered a teardrop attempt to return, [but] aborted under control when it wasn't feasible or safe….I handed control of the plane to my CFI, who nominated our landing spot, and took us safely to a grass off-field landing ….

Investigation reveals the most likely cause …. a bad exhaust valve that was coated with carbon/exhaust debris and was not opening or closing completely, thus limiting the power of the #4 cylinder. That back pressure prevented the other cylinders from being able to develop full power …. a condition that was a result of normal wear and tear and age.

Thomas replied: “Excellent summation of a frightening event.  There are several very good LESSONS there, and some good piloting decisions. Is there anything that in retrospect you think you (or your CFI, or the mechanic) should have done differently?”

The student pilot responded:  “…. I think the A&P mechanic should have been far more interested in the power loss incident previously noted …. I am prepared to accept that stuff happens that you can't explain, but you need then to pass the problem higher up…. and I really think that there is room, even in a Cherokee, for an Engine Management System with a data logging function…. I am pretty sure the issue would have been visible as a change in EGT….I can't say I feel my CFI could have done anything [different], and I was pleased that there wasn't the slightest hint of panic or fearfrom either of us ….”

Thomas’ comments:

• Great job both by your instructor, and you as well. It’s gratifying that you turn this into a learning experience…. instead of turning away from the grounded Cherokee and never looking at airplanes again. Perhaps you have a future as a great flight instructor.

·      Carb icing occurs at far higher temperatures than many pilots suspect; it is more related to humidity than the outside air temperature alone …. it sounds that the mechanic and your instructor had determined conditions were not right for carburettor icing. In that case, they fell into the collective trap of noting a problem and choosing an explanation …. that would let them feel good about doing nothing further to investigate the cause.

·      This is a common decision-making outcome …. It affects all disciplines, not just aviation …. Humans seek simple solutions, and often filter facts to make their solutions fit …. anyway, your mechanic and instructor saw nothing obvious to explain the earlier indications, and being quite human chose to accept a solution without investigating further. 

·      As a pilot for over 30 years …. I’ve found that squawks very rarely fix themselves…. they tend to reappear and get worse at the worst possible moment.

• Most emergency training …. focuses on total engine failures. …. yet partial power loss is three times more likely than total loss of thrust during and immediately after take-off. Recognizing and responding to a partial loss of power is more challenging, because the loss of thrust …. may make you think you have more options than you do because not all of the power is gone
• Your CFI told you to pitch down …. smart instructor! FLYING LESSONS readers should be familiar with the need to PUSH and HOLD when experiencing a loss of power (partial or total) immediately after take-off …. as well as the idea of briefing a departure alternate, that is what airport you’ll aim for if there is a problem that requires you to land but that may permit landing on an airport.
• We’ve also reviewed the idea of trying to turn toward a better landing spot in the event of power loss, but to pre-establish a minimum altitude [at which] you stop turning and accept the best option that is generally straight ahead. It sounds like your instructor is teaching those same LESSONS. 

• You favour engine monitoring systems…. I agree; but installing the monitor alone will not allow you to detect discrepancies …. it requires someone who knows how to interpret [the data] …. pilot training does not usually develop this sort of expertise. 

• You said there wasn't the slightest hint of panic or fear….That’s a sign of [good] mindset and preparation …. Red Bull Racing pilot Matt Hall says that honestly he did not feel an adrenalin rush when he flew fighters and does not now when he flies in Red Bull Air Races …. adrenalin is a physical reaction to fear and surprise, and a properly planned flight will only very rarely present something unexpected …. “An adrenalin rush” Matt concluded “is a sign of poor flight planning.”
• “We immediately entered a teardrop attempt to return, [but] aborted under control when it wasn't feasible or safe.” That’s what it’s all about. Well done. Thank you, Steve T, for letting us learn from you even as you just begin to learn yourself. Best of luck, and skill,as you continue your training!”

– thanks again Tom!

FLY SAFE!