F-14A cross bleed start

[AH_Solid_Snake]

I recently got a chance to start playing through Reflected Sim’s Zone 5 campaign (great btw) and was finding at Nellis in order to start the left engine using the right   engine as the air source took significant throttle movement.

Firstly is this normal? The right engine has completely started and air source is R Eng, external air and power off. In this state the tapes for RPM on the left engine do not move at all in Idle and it takes a little over MIL notch on the throttle quadrant to get it started.

This presents the second question - at this power setting to avoid rolling I have to hold in the toe brakes, but my understanding of the brakes is that the parking brake is the same braking system, just “held on” so why is one more able to hold me stationary over the other?

[The_Tau]

Same issues for me

[sLYFa]

It seems like a single engine's bleed air output is not enough to adequately crank the other one during cross bleed starts. That apparently was also an issue IRL since NATOPS advises to move the throttle up to 75% (I've even heard 87% but can't find a source on that) on the supply engine. In DCS however, the cranking engine will barely reach 18% with the supply engine at 75-80% in the B. In the A, I can't seem to achieve anything above 10%-12%  even with the supply engine at 85% (any higher than that, the plane starts rolling). You can however still start the engine without risking a hot start (at least I have yet to see one in DCS).

Edit: NATOPS indeed states  87% on the supply engine for crossbleed starts for airframes not incorporating a certain airframe change.

Edited November 30, 2021 by sLYFa

[draconus]

On 11/30/2021 at 5:57 PM, sLYFa said:

...hot start (at least I have yet to see one in DCS).

Afair Su-25T can smoke engine if you keep your throttle high during startup.

I usually do xbleeds in Tomcat but have to keep the brakes manually and gently push the throttle until it's enough to spool up.

[sLYFa]

4 hours ago, draconus said:

 usually do xbleeds in Tomcat but have to keep the brakes manually and gently push the throttle until it's enough to spool up.

I've noticed that you have no brakes at all before the comb system comes up allthough you should get brake pressure from the aux/park accumulators. No matter what, the plane starts rolling above 80% unless I 'pre-crank' at lower rpm to charge the comb system. 

[Slant]

On 12/2/2021 at 1:29 AM, sLYFa said:

I've noticed that you have no brakes at all before the comb system comes up allthough you should get brake pressure from the aux/park accumulators. No matter what, the plane starts rolling above 80% unless I 'pre-crank' at lower rpm to charge the comb system. 

And now you know why that's procedure.

[sLYFa]

Its procedure to test the bi-di, nothing to do with building up brake pressure. Aux and park brake accumulators should be pressurized before starting the engines in the first place, not to mention wheel chocks.