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 Post subject: Engine idle
PostPosted: Wed Apr 25, 2018 3:37 am 
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Master Sergeant
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Location: LBSF
Hello,

In Spitfire Mk.I, it seems engine cannot idle well with fully closed throttle. When I pull back the throttle and close it, engine starts to cough, stutter and puff black smoke from unburnt fuel. I've been left stranded at the end of the runway multiple times after landing, where I left the engine to idle for too long during ground roll. :shock: Is this normal for those early Merlin engines :?:

Cheerz,
Will

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 5:23 am 
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Mine has the same behavior and especially with the fixed pitch prop it’s hard to keep the engine running at roll out. But I seem to recall that I either read it in the manual or the forums somewhere that this is absolutely normal an realistic behavior. What I do is raise the rpm ever so slightly that she won’t die on me at the end of the runway :wink:

Happy flying

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 6:21 am 
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Location: Oksbøl, Denmark
As far as I know this is correct, simply don’t close the throttle completely.

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J3 Cub, T6, Connie, P-40, V35B


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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 7:00 am 
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A2A Spitfire Crew Chief
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Location: The South West of the large island off the north coast of Tasmania
Hi Guys,

You should be able to close the throttle momentarily, while stationary, without the Merlin stopping but it
will complain horribly and you will oil up the plugs very quickly. This is exactly how the A2A engine behaves.

From the Spitfire I Manual
Clearing engine after prolonged slow running :- If the take-off is delayed for any reason, the engine should not be allowed to idle too slowly, and should be "cleared" by opening up to moderate r.p.m against the brakes, care being taken to hold the stick fully back, and not to raise the tail by opening up to too high a power. Ensure that the maximum temperature limit is not exceeded (120C).

regards

Darryl

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Last edited by Killratio on Wed Apr 25, 2018 7:22 am, edited 3 times in total.

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 7:13 am 
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Thanks guys!
This is what I will do - put to full close (the throttle) and then open it a bit. The problem is I got too distracted with the radiator on landing and by the time the speed bleeds off - the engine is dead too. That is a part of piloting skills I guess - not to get distracted and stay focused on your duties as a pilot. 8)

Cheerz,
Will

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 7:21 am 
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A2A Spitfire Crew Chief
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Joined: Tue Jul 29, 2008 11:41 pm
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Location: The South West of the large island off the north coast of Tasmania
Yes, but always remember not to panic too much if you boil for a bit when you do land and taxi back.... even the best do that ... (well, maybe not ME :) :) :) )

I heard a great comment by one of the old ATA female pilots the other day, who described the Spitfire as a "Lady in the air..but a Bitch on the ground"

I nearly wet myself :)

BTW, if you ever get the chance to see the documentary "Secret Spitfires" take it!! It is about the production dispersal after Eastleigh got bombed.

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 9:40 am 
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I am reading the Spit manual for the second time as I saw your post Daryl. I guess one needs to refresh their knowledge after GA flying. :mrgreen:

Quote:
From the Spitfire I Manual
Clearing engine after prolonged slow running :- If the take-off is delayed for any reason, the engine should not be allowed to idle too slowly, and should be "cleared" by opening up to moderate r.p.m against the brakes, care being taken to hold the stick fully back, and not to raise the tail by opening up to too high a power. Ensure that the maximum temperature limit is not exceeded (120C).
:wink:

Cheerz,
Will

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 10:14 am 
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Location: Typically hanging around N07, 12N, KLDJ, KCDW
The exact same procedures apply to any piston powered aircraft. Idling at minimum rpm is going to cause lots of troubles, and idling in general can result in overheating, fouling, electrical discharge. One had to shift gears mentally and pay attention. Prior to flight, it is best to check everything to ensure that the engine is ready for flight.

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 10:42 am 
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Oracle427 wrote:
The exact same procedures apply to any piston powered aircraft. Idling at minimum rpm is going to cause lots of troubles, and idling in general can result in overheating, fouling, electrical discharge. One had to shift gears mentally and pay attention. Prior to flight, it is best to check everything to ensure that the engine is ready for flight.


Hi,

I was mentioning this since after run up, some checklists suggest to idle the throttle and see how engine behaves. In example the Mustang, the Cessnas and the Cherokee along with the Cub and the T-6 do not tend to quit while in idle for several seconds, but hold steady low rpm.
On the other hand the Spit's Merlin engine doesn't seem to like throttle idle even for the shortest time. :)

Cheerz,
Will

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 7:09 pm 
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Location: Wales
Had a motorcycle in the 80s that refused to idle. Very cammy engine. It needed constant blipping to keep her going when at a standstill. I use a similar but slower technique with the Spitfire. Easy when you get to know her. :wink:

Steve.

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 Post subject: Re: Engine idle
PostPosted: Wed Apr 25, 2018 7:58 pm 
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LZ-WIL wrote:
Oracle427 wrote:
The exact same procedures apply to any piston powered aircraft. Idling at minimum rpm is going to cause lots of troubles, and idling in general can result in overheating, fouling, electrical discharge. One had to shift gears mentally and pay attention. Prior to flight, it is best to check everything to ensure that the engine is ready for flight.


Hi,

I was mentioning this since after run up, some checklists suggest to idle the throttle and see how engine behaves. In example the Mustang, the Cessnas and the Cherokee along with the Cub and the T-6 do not tend to quit while in idle for several seconds, but hold steady low rpm.
On the other hand the Spit's Merlin engine doesn't seem to like throttle idle even for the shortest time. :)

Cheerz,
Will

Yes this is done to check if the engine has a proper idle rpm. If the idle is too high with the throttle pulled all the way out you’ll have trouble getting a short flare sinc ethe engine will provide some power. But you only check and then raise the rpm back to 800-1000pm on most GA aircraft. It’s different than in cars since in a car you’ll have a clutch to disconnect the drive train from the engine.

Happy flying

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B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B


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 Post subject: Re: Engine idle
PostPosted: Thu Apr 26, 2018 6:44 pm 
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The lowest throttle setting a car needs is "Idle". The lowest throttle setting an aeroplane needs is "Minimum Thrust", which is lower than idle.

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