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Brakes don't hold plane stationary on engine-run up


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Posted

Apparently the wheel brakes should be able to hold the aircraft at zone 1 stage of AB on both engines with cold brakes (as far as I know... DCS doesn't simulate hot or cold brakes)... Currently in DCS the brakes don't even hold you at MIL on a runway, you just start slowly rolling forward. Provided we have carbon brakes on our late A model currently, because they apparently changed the brakes they used throughout the years of service of the Tomcat.

"The capacities of the wheelbrake assemblies are
sufficient to restrain the aircraft in a static condition on a dry
surface with zone No. 1 afterburner (nozzle position 2) set on
both engines. The minimum hydroplaning speed for the main
tires on a wet runway is approximately 90 knots."

"The static torque of carbon brakes is significantly less
than earlier brakes used on F−14A aircraft at the same
hydraulic supply pressure. Therefore, the pilot must press
much harder on the brake pedals to hold the aircraft static at
high−power settings. With cold carbon brakes, approximately
75 to 100 pounds of pedal force will hold the aircraft in a static

condition with zone 1 afterburner (nozzle position 2) set on
both engines. If carbon brakes have been heated up by a
full−stop landing, and for about 45 minutes thereafter, they
will probably not hold the aircraft static with military power
set on both engines even with the parking brake set. In this
case, 75 to 100 pounds of pedal force will hold the aircraft
static with zone 1 afterburner (nozzle position 2) set on one
engine and idle power set on the other. In all cases, holding
the aircraft static at high power settings depends on adequate
runway and tire conditions. Degraded conditions such as wet
runways or worn tires may result in tire skid at high power
settings."

I tried both on the A, setting the power to zone 1 on both engines while holding the brakes down... Plane starts sliding.

Tried holding brakes down while powering only 1 engine to zone 1 and kept the other at idle and alternated between the left and right engine... Still sliding and now the nose points in a different direction too.

Tried just having brakes on and both engines at MIL and the plane slides too.

Dunno if intended behavior or if WIP or what, just letting you guys know what I observed. Didn't have any degraded conditions of wet runway, etc... Maybe I had worn tires?

I tried it also for the B model, and same behavior happens, can't hold it at MIL on both engines and can't hold it with 1 engine at AB and the other idle

"The capacities of the wheelbrake assemblies are
sufficient to restrain the aircraft in a static condition on
a dry surface with 20-percent AB set on both engines.
The minimum hydroplaning speed for the main tires on
a wet runway is approximately 90 knots."

"The pilot must apply maximum pressure on the
brake pedals to hold the aircraft static at MIL. If carbon
brakes have been heated up by a full-stop landing, and
for about 45 minutes thereafter, they will probably not
hold the aircraft static with military power set on both
engines even with the parking brake set. In this case, 75
to 100 pounds of pedal force will hold the aircraft static
with afterburner set on one engine and idle power set on
the other. In all cases, holding the aircraft static at high
power settings depends on adequate runway and tire
conditions. Degraded conditions such as wet runways
or worn tires may result in tire skid at high power
settings."

Posted (edited)

In this video the pilot holds the brakes and powers up for take-off... You can also see that in DCS our nose strut doesn't compress on wheel brake application or when brakes are held also on power up

So, 2 points... The wheel brakes don't hold the plane on take-off when power applied and the nose strut is missing its compression component when brakes are applied during taxi as well as when they are applied for power-up on take-off (looks similar to kneeling for a cat shot, but far less displacement and when brakes released the nose strut immediately springs up releasing its compression)

also, on the take-off roll the launch bar seems to quite vibrate a bit... No such effect in DCS currently, it is on there rock solid.

Edited by Baz000
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