Engine restart speed
Thread Starter
Engine restart speed
Is there such a thing as a best speed for restarting an engine? I have read of techniques for restarting hand-propped aircraft in flight, but for anything with a starter motor does it really matter?
Would anybody here have advocated trying to restart the engine at any point for the first accident discussed?
Moderator
I find Mr. three stripes to be marginally persuasive at best. The thing she said, which I believed the most was: "I don't know". I'd go with that for a lot of what he said.
There is no published airspeed for an inflight restart of a stopped Cessna engine. It's actually pretty hard to get mechanically sound Cessna 152 engine to stop turning in flight. So, if the engine actually stops completely, I would be suspecting a mechanical failure inside. Sure, at any airspeed you like, try the electric starter, if it's going to run, that's a really good first step. If the starter won't turn it over, I'd be setting up for a forced approach. Though Cessna POH's do specify an airspeed following engine failure, that's for optimum glide, 60 knots is not going to windmill start a stopped Lycoming engine with decent compression. They do say that if the engine has stopped, to use the starter.
Turbine engines are different, and do have start envelopes, which may include a specified airspeed.
There is no published airspeed for an inflight restart of a stopped Cessna engine. It's actually pretty hard to get mechanically sound Cessna 152 engine to stop turning in flight. So, if the engine actually stops completely, I would be suspecting a mechanical failure inside. Sure, at any airspeed you like, try the electric starter, if it's going to run, that's a really good first step. If the starter won't turn it over, I'd be setting up for a forced approach. Though Cessna POH's do specify an airspeed following engine failure, that's for optimum glide, 60 knots is not going to windmill start a stopped Lycoming engine with decent compression. They do say that if the engine has stopped, to use the starter.
Turbine engines are different, and do have start envelopes, which may include a specified airspeed.
Restarting a stopped prop in flight was a demonstration item when I started flying in my youth in the DHC-1 which had no starter. The first impression was how hard it was to get the prop to stop, the second was the amount of nose down and speed to get the thing to begin rotating again.
Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,573
Received 415 Likes
on
218 Posts
The RAF CFS course taught me that the best way to rotate a stopped engine in flight is to pitch the aircraft hard. It’s to do with the change in the angle of air flow past the blades. Obviously, you need some excess energy in the airframe to do that.
I can recall at least two personal experiences in the Bulldog when the engine stopped during spin training. The prop began rotating again during the recovery (i.e. pitching nose up from the steep descent) once the spin had been stopped. It was by no means uncommon; RAF guidance was to ignore the stopped engine and concentrate on the spin recovery, simply because it might restart itself during the recovery in that way.
I can recall at least two personal experiences in the Bulldog when the engine stopped during spin training. The prop began rotating again during the recovery (i.e. pitching nose up from the steep descent) once the spin had been stopped. It was by no means uncommon; RAF guidance was to ignore the stopped engine and concentrate on the spin recovery, simply because it might restart itself during the recovery in that way.
Join Date: Jul 2001
Location: maidenhead, UK
Posts: 42
Likes: 0
Received 0 Likes
on
0 Posts
Restarting a stopped prop in flight was a demonstration item when I started flying in my youth in the DHC-1 which had no starter. The first impression was how hard it was to get the prop to stop, the second was the amount of nose down and speed to get the thing to begin rotating again.
An interesting extract from the Robin 2160 POH:
"In a spin of more than 3 rotations, the engine is likely to stall. This raises no difficulty: the propeller should windmill once airspeed is restored and restart the engine.
(CAUTION: engage engine starter only if propeller stops rotating)"
The Robin 2160 has a fixed pitch propeller and a Lycoming 160 hp engine. The above strongly infers that the propeller will be caused to rotate at very low speeds.
"In a spin of more than 3 rotations, the engine is likely to stall. This raises no difficulty: the propeller should windmill once airspeed is restored and restart the engine.
(CAUTION: engage engine starter only if propeller stops rotating)"
The Robin 2160 has a fixed pitch propeller and a Lycoming 160 hp engine. The above strongly infers that the propeller will be caused to rotate at very low speeds.
Last edited by Fl1ingfrog; 19th Sep 2020 at 14:54.
Join Date: Sep 2020
Location: Under the stairs
Posts: 25
Likes: 0
Received 0 Likes
on
0 Posts
To restart a hand start prop in flight involves a dive to near Vne and a hard pull to left or right depending on the rotation of the engine. It works, but uses some altitude up!!
Moderator
a dive to near Vne and a hard pull
It’s a long time since I’ve done it, but used to do demo and practise of restarting in flight without using the electric starter in C152 aerobatic when teaching for the old AOPA aerobatic certificate (in the U.K.). To stop the engine windmilling you had to get the airspeed back almost to the stall, and to get it over compression to start windmilling again needed a dive to about 140 kts, if I remember rightly. Obviously used to do this at about 5000 ft over the airfield, just in case for any reason it wouldn’t restart. Fortunately it always did...
Join Date: Jan 2005
Location: Hotel this week, hotel next week, home whenever...
Posts: 1,492
Likes: 0
Received 0 Likes
on
0 Posts
As part of the FI course before things got “health and safety conscious” I would get the student to stop the prop “for the experience.” C152 with Lycoming.
To actually get the thing to stop rotating you’d have to slow to about 40kts before it would shudder to a halt. It was a good opportunity to compare the difference in ROD between idle/rotating and stopped. Not much in it.
To get the thing rotating again it would require about 110-115kts - which few students appreciated the pitch angle required to achieve.
We’d have a hard deck of 3,000’ which if we weren’t rotating by then then a quick flick of the starter would usually resolve the issue and we’d always be within gliding distance of an RLG/good sized field for a PFL. Never required that bit though.
In the Duchess the manual stated an air start would require 104 (?) before the blue lever forward but always found about 114 meant the accumulator worked so much better. Air starts without the accumulator were horrible - seemed to vibrate for hours until the blade settled down again.
To actually get the thing to stop rotating you’d have to slow to about 40kts before it would shudder to a halt. It was a good opportunity to compare the difference in ROD between idle/rotating and stopped. Not much in it.
To get the thing rotating again it would require about 110-115kts - which few students appreciated the pitch angle required to achieve.
We’d have a hard deck of 3,000’ which if we weren’t rotating by then then a quick flick of the starter would usually resolve the issue and we’d always be within gliding distance of an RLG/good sized field for a PFL. Never required that bit though.
In the Duchess the manual stated an air start would require 104 (?) before the blue lever forward but always found about 114 meant the accumulator worked so much better. Air starts without the accumulator were horrible - seemed to vibrate for hours until the blade settled down again.
I used to have an old Petter Stationary engine, with a BTH Impulse Magneto which was timed for a spark at tdc. It would start from zero speed, just pull the flywheel slowly over compression, and 'Bump' the thing would start.
Most Magneto GA aircraft retard the Impulse ignition below slow idle speed to tdc. So as long as the engine doesn't leak it's compression, it might just start if the prop is pulled slowly over tdc compression.
.
Most Magneto GA aircraft retard the Impulse ignition below slow idle speed to tdc. So as long as the engine doesn't leak it's compression, it might just start if the prop is pulled slowly over tdc compression.
.
Join Date: Sep 2020
Location: Under the stairs
Posts: 25
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Jul 2014
Location: Scotland
Posts: 349
Likes: 0
Received 0 Likes
on
0 Posts
Do not recall the hard pull to left or right bit, but remember reading that restarting a (hand-start) VW engine in flight lost so much height (with no guarantee of success) that it was usually much better to use the height to plan and execute a good forced landing without power. I suppose exceptions would be over water out of gliding range of land, over really hostile terrain or with LOTS of height, However, generally, this sounds like good advice to me.
Join Date: Sep 2004
Location: Down at the sharp pointy end, where all the weather is made.
Age: 74
Posts: 1,684
Likes: 0
Received 3 Likes
on
3 Posts
As part of the FI course before things got “health and safety conscious” I would get the student to stop the prop “for the experience.” C152 with Lycoming.
At the same place I did my course, I suspect. It took all of the space from 6,000' to 3,000' to get the stopped prop over the compression, even then at almost VNE and rocking back and forth to get just the right AoA. Demo'd by the FIC instructor, not practiced by the student (me). One of the stand-outs (amongst many) from the course. The actual advice was 'if the prop has stopped and the electric start won't work, secure the engine (mixture ICO and mags off) and carry out a forced landing without power, forget about trying to restart using airflow'. The demo was all about how hard it is to restart, not how to do it.
TOO
I used to do type-conversions for glider pilots in a Motorfalke motor glider. It had a very reliable VW-conversion, with electric start, that worked first time, every time, provided you remembered to pull the choke out, if the engine was cold.
However, as part of the conversion process, we were required to do dive starts, in case the starter had failed. To start the engine required a very alarming nose-down attitude and a speed of 70-80 kts before the prop would turn over. I vaguely recollect that the height loss was more than 1000'. Vne was 100 kts.
However, as part of the conversion process, we were required to do dive starts, in case the starter had failed. To start the engine required a very alarming nose-down attitude and a speed of 70-80 kts before the prop would turn over. I vaguely recollect that the height loss was more than 1000'. Vne was 100 kts.
Engine Start Procedure:
1. Ensure mirror pointing to correct place to see propeller.
2. Crack open nose air vent – otherwise nose pitot gives excessive position error; it’s in the vent air intake.
3. Operate pneumatic switch to change from fin mounted Pitot to nose Pitot.
4. Operate pneumatic switch to increase variometer damping.
5. Lower undercarriage in case engine fails to start.
6. Ensure fuel cock is on.
7. Turn on ignition.
8. Fly at between 49 and 65 kts.
9. Move engine switch to up position to raise engine.
10. Wait for green LED to indicate engine in raised position. It should be visible in the mirror.
11. Press and hold down electric fuel pump button. Simultaneously pull decompression handle – this should result in propeller hub rotation and any of the five blades still folded unfolding. If any blades still folded waggle rudder to help unfold them.
12. Increase speed to about 65 to 70 kts. Release decompression handle. Monitor via mirror.
13. If engine starts release fuel pump button when rpm stable.
14. If rotation stops back to 11 and try again – with higher airspeed up to 76 kts permitted.
15. If started climb away at 49 to 54 kts (blue line at 51 kts) and raise undercarriage – otherwise land if below your safety height.
Clearly this is a glider procedure doing an air start without an electric starter. Expected height loss around 200' I test the motor for about 10 seconds at the start of every cross country flight once airborne. I won't bore you with the shutdown procedure.
Before beginning the 'starting the motor' procedure one should have found a suitable landing place, and be positioning to land whilst starting the engine - in case it fails. Workload is moderately high.
Flight Manual says,"Below 300 m (984') AGL, starting attempts are to be avoided so as to have a safe height for plannig the approach pattern should the engine fail to run."
1. Ensure mirror pointing to correct place to see propeller.
2. Crack open nose air vent – otherwise nose pitot gives excessive position error; it’s in the vent air intake.
3. Operate pneumatic switch to change from fin mounted Pitot to nose Pitot.
4. Operate pneumatic switch to increase variometer damping.
5. Lower undercarriage in case engine fails to start.
6. Ensure fuel cock is on.
7. Turn on ignition.
8. Fly at between 49 and 65 kts.
9. Move engine switch to up position to raise engine.
10. Wait for green LED to indicate engine in raised position. It should be visible in the mirror.
11. Press and hold down electric fuel pump button. Simultaneously pull decompression handle – this should result in propeller hub rotation and any of the five blades still folded unfolding. If any blades still folded waggle rudder to help unfold them.
12. Increase speed to about 65 to 70 kts. Release decompression handle. Monitor via mirror.
13. If engine starts release fuel pump button when rpm stable.
14. If rotation stops back to 11 and try again – with higher airspeed up to 76 kts permitted.
15. If started climb away at 49 to 54 kts (blue line at 51 kts) and raise undercarriage – otherwise land if below your safety height.
Clearly this is a glider procedure doing an air start without an electric starter. Expected height loss around 200' I test the motor for about 10 seconds at the start of every cross country flight once airborne. I won't bore you with the shutdown procedure.
Before beginning the 'starting the motor' procedure one should have found a suitable landing place, and be positioning to land whilst starting the engine - in case it fails. Workload is moderately high.
Flight Manual says,"Below 300 m (984') AGL, starting attempts are to be avoided so as to have a safe height for plannig the approach pattern should the engine fail to run."
Moderator
1. Ensure mirror pointing to correct place to see propeller.
, perhaps Jim59 would tell us which airplane these interesting instructions apply to!
metal bladed engines were harder to air start than wooden bladed ones.
If you wish to restart a `stopped` prop in flight,by diving,is it better to open the throttle fully,or keep it closed...
Join Date: Nov 2005
Location: Zulu Time Zone
Posts: 730
Likes: 0
Received 0 Likes
on
0 Posts
to get it over compression to start windmilling again needed a dive to about 140 kts,