Cold start: Torque rises when applying fuel flow lever

[Usagi]

Hi,

what causes torque to rise rapidly when opening fuel flow lever slowly during startup?

• I wait until rpm reaches idle around 25000
• rotor brake off, slowly moving fuel flow lever until rotor starts moving
• wait until rotor rpm syncs with turbine (torque will be around 20%)
• slowly move fuel flow lever: Torque will rise quickly and reaches 100%

I haven't found any mentions in the checklists and startup guides.

[MAXsenna]

Hi,
what causes torque to rise rapidly when opening fuel flow lever slowly during startup?

• I wait until rpm reaches idle around 25000
• rotor brake off, slowly moving fuel flow lever until rotor starts moving
• wait until rotor rpm syncs with turbine (torque will be around 20%)
• slowly move fuel flow lever: Torque will rise quickly and reaches 100%

I haven't found any mentions in the checklists and startup guides.

That shouldn't happen and it seems you perform the correct procedure. Double check that you don't have any axis conflicts/have bound another axis to the fuel lever. That's my guess.
Cheers!

Sent from my SM-A536B using Tapatalk

[Usagi]

1 hour ago, MAXsenna said:

That shouldn't happen and it seems you perform the correct procedure. Double check that you don't have any axis conflicts/have bound another axis to the fuel lever. That's my guess.
Cheers!


 

It is actually axis related.

I don't have any conflicts there, it is enough to bind fuel flow lever to axis. It behaves like collective is applied simultaneously with fuel flow lever.
The controllers overlay however shows that collective is at zero.

[MAXsenna]

It is actually axis related.
I don't have any conflicts there, it is enough to bind fuel flow lever to axis. It behaves like collective is applied simultaneously with fuel flow lever.
The controllers overlay however shows that collective is at zero.

Have you configured the axis as a slider?

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[Usagi]

41 minutes ago, MAXsenna said:

Have you configured the axis as a slider?

 

Yes I have.
I can kind of a make startup when I move the lever somewhat quickly. The slower the movement, the more time the torque has to rise above 100%.
If I open fuel flow lever quite fastly, the rpms won't sync but rotor rpm reaches it's normal range and torque drops from some 70-90% to 20%

Weird.

[MAXsenna]

Yes I have.
I can kind of a make startup when I move the lever somewhat quickly. The slower the movement, the more time the torque has to rise above 100%.
If I open fuel flow lever quite fastly, the rpms won't sync but rotor rpm reaches it's normal range and torque drops from some 70-90% to 20%

Weird.

Right! Haven't flown it in a while, but I always move it slow, to not break it.

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[Usagi]

So my solution is to move it quite fast as after rpm reaches 42000 or more (while not being synced), the torque drops to the 20%

By moving slow, torque rises constantly and reaches 100% and way more. Really strange.

[Volator]

@Usagi

So I checked the torque issue on cold start and did not experience what you are describing. Torque went up to 50% max during engine run-up, see track attached.

Quote

always move it slow, to not break it.

This is the way.

 

SA-342_torque_test.trk

Edited April 15 by Volator

[Usagi]

On 4/14/2025 at 8:33 PM, Volator said:

@Usagi

So I checked the torque issue on cold start and did not experience what you are describing. Torque went up to 50% max during engine run-up, see track attached.

This is the way

Thank you!

The reason why I had so much troubles with a lever on real controller is that when moving with mouse you do it somewhat slower. When using lever (on controller) it feels like you do it slowly and nothing happens until fuel lever is almost opened (5/6 of the movement is used). Then rotor blades begins to move.

 

After watching this track, I did first part of lever movement really slowly and by doing that, the rotor blades begun to move in early phase and torque never went above 50%

 

Here's track that shows what happens. In the first startup, the lever is already pushed quite far until blades starts to turn, turbine rpm is already around 35k

In the second attempt in the track, the turbine rpm reaches only 30k when blades begun to turn (ignore accidental lever back and forth movement).

SA-342_lever_test.trk

 

The second track shows the workaround I found. It shouldn't be possible, but if fuel lever is almost open when blades starts to turn and torque begins to rise, just ram the lever forward. The rpm goes up and torque goes down.
I don't know if this causes some engine problems? Haven't flown more than couple of tens kilometer missions by starting this way.

SA-342_lever_just_ram_it.trk

 

[Volator]

1 hour ago, Usagi said:

The second track shows the workaround I found. It shouldn't be possible, but if fuel lever is almost open when blades starts to turn and torque begins to rise, just ram the lever forward. The rpm goes up and torque goes down.
I don't know if this causes some engine problems? Haven't flown more than couple of tens kilometer missions by starting this way.

I once had an EGT runaway condition when I moved the throttle too fast; I think the Gazelle simulates engine damage (I once experienced it due to dust and no filter), so you might want to be careful with that technique