Multi-engine training mixture cuts
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Having read all of the above posts, I believe flyby_kiwi has made the overriding statement (albeit he was trying to make the opposite point) when he said "wouldn't do it in a single though". He has made an extremely good point. One must ask themselves why not in a single? The most obvious answer is that thay wouldn't because they are not prepared to risk the engine not starting again. As a grade one instructor and previous ATO who has used both methods in the past, I have now adopted the Throttle failure technique below approx 1500' as a risk management technique. I derived this idea from researching a number of official Continental and Lycoming sources directly asking specific questions relating to damage to counterweights and backpressure issues associated with the Throttle technique. It became apparent that these are only considerations if the throttle is "chopped" closed at a rapid rate.
As has been mentioned before, multi engine training requires a particularly critical amount of risk analysis between the "reality" of training scenarios vs. considerations of a/c or engine damage, terrain clearance, allowing instuctor and student a safety buffer, and good communication.
I hope this has added something worthwhile to the discussion and congratulations must be offered to centaurus for opening up an issue that is sadly now more poignant in light of a recent fatal training accident.
As has been mentioned before, multi engine training requires a particularly critical amount of risk analysis between the "reality" of training scenarios vs. considerations of a/c or engine damage, terrain clearance, allowing instuctor and student a safety buffer, and good communication.
I hope this has added something worthwhile to the discussion and congratulations must be offered to centaurus for opening up an issue that is sadly now more poignant in light of a recent fatal training accident.
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Spotlight
Well Id beter get out of the engine shop then!!!!I thought Id won something! being a winner and all that.If im wrong(good chance) tell me soo with something logical.!!Isnt everthing at spotlight, CHEAP!!!!!!!!
Well Id beter get out of the engine shop then!!!!I thought Id won something! being a winner and all that.If im wrong(good chance) tell me soo with something logical.!!Isnt everthing at spotlight, CHEAP!!!!!!!!
The primary reason lead is in fuel is to increase the octane rating of the fuel. The octane rating is a measure of the fuel's ability to withstand 'knocking' (detonation).
The reason Gottem's ute loves 100LL is that as a higher octane fuel you can run the engine at a higher compression level and extract more power from the fuel.
The fact that the lead is supposed to lube the valve guides is a secondary effect (and its debatable whether there is any benefit) and its absence for a few minutes at a time will not harm an engine. (Otherwise older cars running on both leaded fuel and LPG would fall apart when running on LPG).
Also these days with the elimination of lead in mogas means none of these older cars which used to run on leaded fuel (and therefor benefiting from any lubrication of valve guides) will have had any lead in their engines for a few years. I havent heard of any mass extinction of pre 84 car engines yet.
Bevan..
The reason Gottem's ute loves 100LL is that as a higher octane fuel you can run the engine at a higher compression level and extract more power from the fuel.
The fact that the lead is supposed to lube the valve guides is a secondary effect (and its debatable whether there is any benefit) and its absence for a few minutes at a time will not harm an engine. (Otherwise older cars running on both leaded fuel and LPG would fall apart when running on LPG).
Also these days with the elimination of lead in mogas means none of these older cars which used to run on leaded fuel (and therefor benefiting from any lubrication of valve guides) will have had any lead in their engines for a few years. I havent heard of any mass extinction of pre 84 car engines yet.
Bevan..
C'mon guys, have another guess. It's quite entertaining to watch the armchair experts at work talking about something they've had no training either in or with (and certainly no QUALIFICATION to do so)!
Who's got the next guess? C'mon down!
Who's got the next guess? C'mon down!
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Hey OPS ,could you please use words i understand!!!Maybe I should have said <The valve stems get some lube from the lead in the fuel air mixture,Now being no car mechanic,Some one did tell me that early cars on LPG had special lube put on valves when installed.Im sure Unleaded fuel you buy at the servo might just have a little something mixed into it to help with lubeing valve stems and valve seats.
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Now there's a good point. Instructors of single engine trainers don't cut the mixture for PFL or engine failure after take off because they figure the engine might not re-start for some reason or other. Good thinking - and very prudent.
In a twin, the same thing should apply. Because if you cut a mixture after take off in a twin and it doesn't re-start when you want it to, then the windmilling prop is going to cause serious drag and the aircraft will be unable to maintain speed and height.
In a twin, the same thing should apply. Because if you cut a mixture after take off in a twin and it doesn't re-start when you want it to, then the windmilling prop is going to cause serious drag and the aircraft will be unable to maintain speed and height.
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The view I had (and may not have made too clear) is that cutting the mixture on one engine in a twin will not completley stop the engine as at the IAS you would be maintaining using the live engine (at least blue line) the 'dead' engine will contine to windmill.
Once the situation is undercontrol and the student has Identified, Verifed and 'Feathered' (only coarsening the dead engine rather than retarding the pitch leaver to the full feather ident) then 'zero thrust' is set by the instuctor invloving reintroducing the mixture and setting the power and pitch settings as per the AFM so the mixture is only left cut for prehaps several seconds.
The reason for (myself anyway) not wanting to use mixture cuts in the single is that usually the a/c will have a slow best glide speed (say 65kts for a C172) and with a relativly green student it isint going to take much distraction him/her before the IAS can be back to 50kts and the prop/engine will stop windmilling altogether.
Interesting views that Ill bear in mind but admittedly had never heard of using the throttle to simultate the failure in a twin untill this thread came about.
Once the situation is undercontrol and the student has Identified, Verifed and 'Feathered' (only coarsening the dead engine rather than retarding the pitch leaver to the full feather ident) then 'zero thrust' is set by the instuctor invloving reintroducing the mixture and setting the power and pitch settings as per the AFM so the mixture is only left cut for prehaps several seconds.
The reason for (myself anyway) not wanting to use mixture cuts in the single is that usually the a/c will have a slow best glide speed (say 65kts for a C172) and with a relativly green student it isint going to take much distraction him/her before the IAS can be back to 50kts and the prop/engine will stop windmilling altogether.
Interesting views that Ill bear in mind but admittedly had never heard of using the throttle to simultate the failure in a twin untill this thread came about.
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I had an engine refuse to re-start a long time ago as a student in a C150. The instructor failed the engine by turning off the fuel shutoff between the seats. I got too slow, the prop stopped, wouldn't restart, and we ended up in a paddock. At least I know I can do a FL now!
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I always got the student to give me a brief on what they would do if they had an engine failure just after take-off and if it didn't include land on the available runway then I would suggest that would be a good thing to consider. I would never simulate a failure below 400' agl simply a matter of self preservation. I used to put the mixture to ICO until the boss ,also the chief LAME, set me straight on the drawbacks of using the mixture instead retarding the throttle.
