Clearing Engine During Practice Forced Approach

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pelmet
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Clearing Engine During Practice Forced Approach

Post by pelmet »

"C-GFYI, a Cessna 172S operated by Montair Aviation, was conducting a local training flight from
Red Deer airport (CYQF), AB. During the training flight the instructor was demonstrating how to fly
a simulated forced approach. During the exercise, the instructor did not perform any engine
warming procedures. When the airplane was approximately 200 feet agl, the instructor applied full
power and there was no response from the engine. The instructor proceeded to land the aircraft in
the field. Upon landing, the propeller stopped wind milling. The airplane received no damage, and
the instructor and student received no injuries. The ELT was not activated. The aircraft magnetos
and sparkplugs were replaced."


So what is the reason you clear the engine(add power briefly) for practice forced approaches. I read something on-line about carb ice but this aircraft has fuel injection. Fouled plugs?
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photofly
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Re: Clearing Engine During Practice Forced Approach

Post by photofly »

My guess is operator error in this case. Who moved what, during the “cause” check? 200 agl is very late to leave it before climbing away.

When practicing forced approaches I do like to apply the power periodically, for confidence. I did once practice a forced approach in an older type new to me that had the mixture control where the typical aircraft has the carburetor heat. The engine did not respond when I applied power (guess why) but I had time to analyze and fix the issue.
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ZBBYLW
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Re: Clearing Engine During Practice Forced Approach

Post by ZBBYLW »

Guess he or she had selected a good field and set up well for it.
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digits_
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Re: Clearing Engine During Practice Forced Approach

Post by digits_ »

photofly wrote:
Sat Sep 28, 2019 4:08 am
200 agl is very late to leave it before climbing away.

Interesting. I think it is quite early. It depends on the area where you practice of course, but in the red deer area there is a lot of nothing. I wouldn't find anything wrong with flying it till the wheels just don't touch the grass. It is often the last part of the approach where students realize they did or did not make the field. I find it very valuable to wait as long as possible.
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photofly
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Re: Clearing Engine During Practice Forced Approach

Post by photofly »

You need to read the TATC case where Transport successfully prosecuted an instructor for low flying during a practice forced approach :-)

I do agree it does depend on the environment. But around here, everywhere is someone's field, and it's really tricky not to pass over a person, vehicle or structure at an unlawful altitude on the way in, or on the way out, if you go too low. Plus, noise complaints make everyone angsty, and when TC enforcement hears from an angry farmer that you were well below whatever altitude you were actually well above, time and again both they and the tribunal members prefer the testimony of the person on the ground with no experience of judging aircraft height or distance over that of the person sitting in front of the altimeter.

If there is doubt as to whether a safe landing can be made, then continue. But in this case, the instructor was flying, so there shouldn't have been any doubt. However, the proof of the pudding may well be in the eating. If they had attempted to climb away earlier, they may not have had to land in the field.
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CpnCrunch
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Re: Clearing Engine During Practice Forced Approach

Post by CpnCrunch »

Maybe forgot to richen the mixture?
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corethatthermal
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Re: Clearing Engine During Practice Forced Approach

Post by corethatthermal »

A cold engine may stutter or die when given an abrupt throttle movement , Everyone knows that !
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youhavecontrol
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Re: Clearing Engine During Practice Forced Approach

Post by youhavecontrol »

From what I understand, its mainly to clear any possible fouling, but also to keep the engine from shock cooling. Often the prop is windmilling faster than a ground idle speed meaning the fuel going into the cylinders has little to push against as it burns. Most engines will sound rather pissed-off at you for applying too much throttle after the engine is cold and full of carbon.
From what I recall you can legally go as low as your company training SOP's allow during forced approach training, so long as you can argue that you did not endanger yourself, others, property, or cause a disturbance. Common sense is important in all cases.
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Re: Clearing Engine During Practice Forced Approach

Post by Aviatard »

youhavecontrol wrote:
Sat Sep 28, 2019 1:15 pm
From what I recall you can legally go as low as your company training SOP's allow during forced approach training, so long as you can argue that you did not endanger yourself, others, property, or cause a disturbance. Common sense is important in all cases.
There is nothing about SOPs or a disturbance in the applicable CARs but the rest is correct. CAR 602.14(2)(b) and 602.15(2)(b).
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youhavecontrol
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Re: Clearing Engine During Practice Forced Approach

Post by youhavecontrol »

Aviatard wrote:
Sat Sep 28, 2019 2:03 pm
youhavecontrol wrote:
Sat Sep 28, 2019 1:15 pm
From what I recall you can legally go as low as your company training SOP's allow during forced approach training, so long as you can argue that you did not endanger yourself, others, property, or cause a disturbance. Common sense is important in all cases.
There is nothing about SOPs or a disturbance in the applicable CARs but the rest is correct. CAR 602.14(2)(b) and 602.15(2)(b).
That could be but if a company states that "No training flights are allowed to operate below xxxx' AGL in training areas X and Y" and a pilot choose to go below that, they are in breach of the company rules that are approved by Transport Canada. Transport Canada definitely looked into noise complaints and "disturbances" caused by my old flight school conducting forced approaches within eye-shot and ear-shot of people. .. usually when someone was creative and flew just outside of the designated training area.
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Re: Clearing Engine During Practice Forced Approach

Post by PilotDAR »

but also to keep the engine from shock cooling
If shock cooling were going to occur, it would have done so when you first closed the throttle too quickly at the top of the glide. After that, and during the glide, clearing the engine is just assuring that when you gently open the throttle again, the engine will respond smoothly as expected. If you ram the throttle (any time) and it quits, you got what you asked for. Throttles never need to be jammed either way.
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Re: Clearing Engine During Practice Forced Approach

Post by C.W.E. »

If you ram the throttle (any time) and it quits, you got what you asked for. Throttles never need to be jammed either way.
It was one of the worst training mistakes I found, and it usually started during the take off part of flight, for some strange reason far to many instructors just rammed the throttle from idle to full power as if the faster you moved it the shorter the take off would be.

Really disturbing habit and it was common.
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Alex335
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Re: Clearing Engine During Practice Forced Approach

Post by Alex335 »

photofly wrote:
Sat Sep 28, 2019 6:30 am
You need to read the TATC case where Transport successfully prosecuted an instructor for low flying during a practice forced approach :-)

I do agree it does depend on the environment. But around here, everywhere is someone's field, and it's really tricky not to pass over a person, vehicle or structure at an unlawful altitude on the way in, or on the way out, if you go too low. Plus, noise complaints make everyone angsty, and when TC enforcement hears from an angry farmer that you were well below whatever altitude you were actually well above, time and again both they and the tribunal members prefer the testimony of the person on the ground with no experience of judging aircraft height or distance over that of the person sitting in front of the altimeter.

If there is doubt as to whether a safe landing can be made, then continue. But in this case, the instructor was flying, so there shouldn't have been any doubt. However, the proof of the pudding may well be in the eating. If they had attempted to climb away earlier, they may not have had to land in the field.
What violation is there for low flying a GA aircraft? I remember some limits form the 6-700 series CARs when doing the CPL theory. 1000’ over built up areas, and 500’ from structures and people was what I thought applied for forced approaches over unpopulated areas like fields. 500’ is really not a very big distance, would be pretty hard to violate these limitations, and likely trigger many noise complaints before being near the legal 500’ separation limit.

Aborting an approach at 500 AGL would make for some very poor training, we normally went down to 20-50’ AGL. Even on my flight test it was down to around 50’ AGL before being instructed to overshoot.
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iflyforpie
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Re: Clearing Engine During Practice Forced Approach

Post by iflyforpie »

Warming an engine helps the fuel to vaporize and mix with the air. The carb and even the mechanical port fuel injectors don’t do a very good job of it. On cars you have (had) a downdraft carburetor which is bathed in engine heat plus the liquid cooled cylinder barrels which retain heat during low power.

Lycomings are a bit better than Continentals in that respect since they mount the carb on the oil pan and run the intake manifold through the oil pan vs all by itself in the airflow. Almost everyone including me has a story of carb ice or engine coughing on acceleration in a Cessna 150 with the O-200 even with carb heat and engine warming.
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Re: Clearing Engine During Practice Forced Approach

Post by Beefitarian »

The spark plugs and magnetos were replaced.

Sounds like there might have been a problem that was beyond carb ice. Maybe it would not even re-start on the ground with the existing plugs.

Were the plugs fouled from the poor thing never having had the mixture leaned other than during the run up check list?
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photofly
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Re: Clearing Engine During Practice Forced Approach

Post by photofly »

It says they were replaced; it doesn’t say why, or why you would replace *all* the plugs and *both* magnetos.

Have you ever heard of both magnetos failing along with 8 plugs, all on the same flight? No? Me neither. Maybe it was a small thermonuclear explosion in the engine compartment.

I’m sure I’m not the only person thinking that there was nothing wrong with the airplane, and the - ahem - maintenance actions described are logbook dressing, or more charitably, comfort actions, and nothing else.
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Re: Clearing Engine During Practice Forced Approach

Post by Beefitarian »

I'll fess up, never seen a single mag fail. I was thinking the plugs might have been fouled. I don't think that would harm the magnetos.
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