Gliding

[hopharrigan]

A question for you instructors concerning gliding in a constant-speed airplane such as a C205. Is there any advantage in setting the prop lever to full decrease in order to reduce drag? Any penalty or risk to the engine? I would guess that the risk comes in a practice forced landing when it comes time to go around, but maybe there is some benefit with a setting part way between full increase and full decrease?
And does anyone know the practical effect of landing gear drag during an engine out approach in these airplanes? The POH says that there is little drag from the gear, would you agree?

[Chuck Ellsworth]

HOPH..

Prop should be full coarse for minimum drag.

There will be less chance of any damage to engine due to less R.P.M.and less reverse loading on engine.

............................................

The hardest thing about flying is knowing when to say no.

:D

[hopharrigan]

Yeah, that's what I thought, but there is nothing in the POH about it.

[Kermit 180]

The EMERGENCYsection of your POH should contain information about the use of CSU and retractable (I presume you meant retractable)undercarriage or landing gear, in the event of a glide resulting from a total loss of engine power. The glide speed is usually subject to given conditions, eg; no flap, gear extended, cowl flaps closed, etc.

A coarse prop may reduce drag and RPM loading as stated in the previous post, but procedures should be in accordance with the POH. It would also be prudent to consider the gear failing to extend, in which case the coarse propellor will be less likely to bend on impact, and could cause your nice little aeroplane to flip on landing.

Food for thought. Best bet is to read your POH thouroughly and consider the variables.

Kermie :)

[ 19 October 2001: Message edited by: Kermit 180 ]

[hopharrigan]

I am soon to do a check ride on a C182RG and one of the things to be covered will be engine failure and forced landings. I have looked at the POH for several Cessna types with variable pitch props and the subject does not come up at all. It seems obvious to me that the less drag the better, at least while gliding to the landing spot, and I wondered why there was no mention of this. I figured it had to be because there was either no drag benefit (or negligible) or some reason why it was not a good idea (engine impacts, cooling, possibility of not recovering during go around, loading of the camshafts or something like it). Thus my question. Any ideas would be appreciated.

[Kermit 180]

If it doesnt mention the propellor position in the event of engine failure, I would leave it.

[M.Mouse]

Long time since I flew a VP prop aircraft but as soon as you have an engine failure will the prop not go to fully fine to try and maintain the engine RPM anyway. Also aren't most VP props oil pressure driven with the default, ie no oil pressure, spring driven to fully fine?

If I am talking tosh please tell me as I genuinely cannot remember clearly from so long ago.

[Stan Evil]

I think MMouse is right. With a real engine failure the prop will either be windmilling fully fine or will have stopped and there's nothing you can do about it. For practice leaving the prop at or near max means a slightly poorer gliding performance than moving it to coarse (about 100 ft/min in an Arrow) but at least you won't accidently blow the thing up when you go around! As far as the effect of gear on the glide is concerned - in an Arrow it makes a hell of a difference if you maintain the published glide speed. However, Mr Piper doesn't publish a gear down glide speed which should be considerably lower as Vmd is reduced so knocking 5 or 10 knots off once the gear is down may give you a reasonable glide.

[hopharrigan]

At idle the engine does slow down a few hundred rpm with full coarse, and there is an effect on the glide as a result. But of course there might not be enough oil pressure to enable the csu to work if the engine is failed. I am not game to shut the engine off to find out!
I also noticed that the glide was better than the POH indicated it would be: the POH gives a glide angle of around 6 degrees but I did not think it was that rapid in fact, more like 4 degrees.
I was hoping someone out there would have done all this before.

[Kermit 180]

Sorry, never done it, never will. Power off glides are not something I would like to experience in a CSU equipped aircraft. Practice engine failures in such aircraft are done with the throttle closed and the pitch full fine. I fail to see the advantage of practising intentional gliding (not FLWOP practice) in a CSU aircraft.

[Kermit 180]

I also add that I have never flown a C182RG, however I have flown a C172RG and have just checked th Cutlass Flight Manual (POH) for details. A total engine failure requires the pilot to attain 75 knots immediately, pick a field, and carry out engine shutdown checks. The gear should be extended but there is no mention of propellor pitch. Hope this helps.

Kermie

[Chuck Ellsworth]

Kermit, I am courious as to your statement that practice engine failures are done with the throttle closed and the pitch full fine.

Please explain why you would need the pitch in full fine?

If you are a flight instructor I am really courious to find out why you would make such a difinitive statement.

Now don't get all excited and take my question as an invitation to argue it's just that I wish you to elaborate a little more as I do not see the need to select full fine pitch just to practice engine outs. Especially if you are paying for the engine overhauls.

............................................

;) The hardest thing about flying is knowing when to say no. ;)

[Kermit 180]

I should have elaborated that I meant the pitch should be full fine for going around from the practice FLWOP. Just as you would for going around normally.