Crossbleed start at IDLE RPM

[Mud]

From what I can gather from natops:

 

Engine crossbleed start on the ground can be accomplished with the throttle on the operating

engine at or above idle rpm.

 

However, when I try this, the left engine won't spool up unless I add quite some power on the right one.

 

Procedure followed:

 

- Ambient temperature 8 degrees C

- Start right engine

- Disconnect ground power and air

- Air source set to right engine

- Crank left engine

 

Am I missing something?

 

Best regards,

 

Mud

[electricaltill]

I don't know, but one of the other inconsistencies I remember being pointed out about the engines was that idle power was sufficient for taxi in the real jet, and isn't here. Might be related?

[sLYFa]

In the real AC, you may need to advance throttles to provide enough bleed air pressure to crank the starting engine to an acceptable speed of about 20%. This happens with hot temperatures and/or low ambient pressure, since the running engine's compressor, from which the bleed air is taken, can not provide enough pressure in these conditions. NATOPS mentions up to 80% rpm for the running engine during crossbleed starts. However, the starting engine should crank regardless of the running engine's power setting, it just may not reach the 20% rpm needed for a succesful start.

In DCS, things appear more simplified, meaning that the engine won't crank at all unless you add some power to the running engine.

Engines also take awfully long to ignite during a crossbleed start in the DCS F-14.

I don't know, but one of the other inconsistencies I remember being pointed out about the engines was that idle power was sufficient for taxi in the real jet, and isn't here. Might be related?

I think this has more to do with how DCS handles friction between the ground and the aircraft. IIRC razbam mentioned that they intentionally increase static friction for their Harrier to prevent it from skidding on a pitching carrier deck, which has the negative side effect that you need more thrust for taxiing. Maybe HB did something similar.

Edited February 5, 2020 by sLYFa

[draconus]

IronMike mentioned earlier that sticky ground is a common problem in sims and DCS is not free of it too.

[fat creason]

On a cooler day like 8 C, it should be able to cross-start with the running engine just above idle.

[Spiceman]

You have to come off the idle stop to enable the cross bleed valve. You shouldn’t need a lot of power, but you have to come off the stop.

[electricaltill]

I mean, looking at that scale on the right side it looks like you need somewhere between 75-80%. Well above idle.

[Spiceman]

The diagram is not meant to show scale. Crossbleed starts should be attempted at the lowest RPM that results in a sufficient windmill RPM. If it’s not sufficient, first increase RPM just enough to close the nozzles on the operating engine. After that increase in 5% increments until it gets the job done.