Windmill airstart

[Flow32]

Hello Everyone !

I was trying some engine air starts, and I have a question where I did not find the answer. If this was discussed already, can you please point me to the correct thread ?

Here is what I tried :

• At high altitude (about 40k feet), place throttle in cutoff position
• Wait for the engine to spool down (< 20% RPM)
• 30° dive to windmill the engine >20% : SEC light turns off
• Place throttle into idle

That would trigger a hot start each time. The only way I had to restart the engine was using the JFS.
I thought it was possible to windmill the engine in order to restart it ?
The only reason I could find was that the total air temperature was too high when windmilling to properly start the engine.

Thank you

[LorikEolmin]

To accomplish an air start:
1. Throttle OFF
2. Airspeed As required

When RPM is 50-25 % with FTIT below 700°C
3. Throttle IDLE, then advance
4. Idle detent Toggle
5. RPM Check increasing

If RPM below 20% with FTIT below 700°C:
3. Attitude Below 20.000 feet and < 400 kts
4. JFS START 2
5. Throttle RPM at 20% min - IDLE, then advance
6. Idle detent Toggle
7. RPM Check increasing
8. Throttle Idle

I’d say no? Other sources?

[Flow32]

Yes I saw the checklist, I was just doing some tests.
I guess that normal procedure would have you use the JFS as windmilling could cost a lot of altitude with no guarantee that it works.

I can get the engine up to 22 - 23% without JFS, which “should” be enough to start it, hence my question

[M79]

@Flow32:

Yes I saw the checklist, I was just doing some tests.
I guess that normal procedure would have you use the JFS as windmilling could cost a lot of altitude with no guarantee that it works.

I can get the engine up to 22 - 23% without JFS, which “should” be enough to start it, hence my question

"Here is what I tried :

• At high altitude (about 40k feet), place throttle in cutoff position"

“3. Attitude Below 20.000 feet and < 400 kts”

[Flow32]

Yes, that is to start the JFS, which I did not do at 40k feet.

[Malc]

It works fine if in parameters:

[LorikEolmin]

I think Flow is trying to windmill the engine without using the JFS. I can’t really be sure from the video, but since it starts right under 20k feet, I suspect you used it?

[luke777]

Air starts are slower and require higher ITT/EGT than ground starts. It might look like an hot start, consider it may be correctly coded.

Sent from my SM-G5700 using Tapatalk

[Malc]

@LorikEolmin:

I think Flow is trying to windmill the engine without using the JFS. I can’t really be sure from the video, but since it starts right under 20k feet, I suspect you used it?

Nope.

[Flow32]

@Malc:

It works fine if in parameters:

Hmm… I could swear I tried that multiple times and always got a hot start. Thank you for the video, I’ll try again and report back.

@luke777:

Air starts are slower and require higher ITT/EGT than ground starts. It might look like an hot start, consider it may be correctly coded.

Sent from my SM-G5700 using Tapatalk

Thanks Kaos ! ITT really went up very high quite quickly. On Malc’s video it looks normal, I got something completely different.

Anyways, thanks guys, I’ll try again maybe tonight and report back, with a video if I can figure it out.

[Huesudo]

For a windmilling restart without JFS, you have to be going pretty damn fast all the way through the process. If at any point your speed drops below 400 kias, the process may fail and you could end up with a hot start.