Idle Thrust

[Dino Might]

Was in Nevada Aerobatics Online just now, trying to refuel on the KC-130. At idle thrust, ~10k AGL, 1000 lbs fuel total, no stores, I was gaining speed and overtaking the tanker every time. Tanker was at about 200 kias. I was able to get into a 5 deg climb and accelerate up to 215 kias, around 13k AGL.

 

Engine RPM went from 43.7% to 45% in the climb. I think I forgot to turn the H2O switch off, but should there be any boost to the thrust at idle regardless of the switch position? Does the water switch position cause an RPM boost at all throttle positions and then H2O only kicks on at 95+ %?

 

May not be a bug, but wondering if this is the right behavior.

[aileron]

Yea, its a good question...

 

I had the h2o switch on trying to refuel at 15,000 ft and couldn't stop accelerating. Once I was done refueling by using my nozzles to slow down. I realized I left the h2o on. :(

[Brewnix]

So in the A1-AV8B-NFM-000 technically opened in Adobe page23.

 

Switch TO or LDG

 

"With the The water injections system armed (engine JPTL datum is changed) and the water injection augmenting bypass valve in the FCU provides supplementry fuel resulting in a 9.5 to 17.% enigine rpm rise at idle."

 

"TO" Also water flows when the throttle is set above 95% rpm. after takeoff water continues to flow until airspeed exceeds 250 knots or water is depleted or throttle moved below 95%

 

"LDG" water flows when airspeed drops below 250 knots and when Jet pipe temps go above 695% the throttle is moved above 95%

Just quoting manual. So I guess trying to refuel make sure its in the "OFF" position. EDIT

Edited January 12, 2018 by Brewnix

[Madbrood]

To be fair, that is mighty slow for the tanker... I usually refuel at circa 240KIAS

[Eagle7907]

Idle Thrust

 

I agree. I usually have tanker set speed somewhere 250 or higher. Makes stability much better and easier to control. Only time I’d think of setting it that low if you were setting up a mission where a much slower aircraft needed to share the same tanker as you.

 

 

Sent from my iPhone using Tapatalk Pro

[Mars Exulte]

200kts is just a hair above stall speed :) Like these other fellows, I have been doing it between 250-300kts @ 15k feet, flaps to cruise (not auto). Note: Attempting to refuel with the flaps disabled entirely is quite difficult, you need the extra drag and lift in order to maintain a stable, low speed and correct AoA. With flaps raised, the Harrier wants to accelerate, even at idle thrust.

 

Keep in mind, just as a reference, the Harrier is like half the size of the A-10, and has a single engine that outputs more thrust than BOTH engines on the A-10 combined. In fact, the manual specifically says to direct nozzles partially downward when on the ground because even at idle it has enough thrust to propel the aircraft if the brakes are not engaged.

 

It's a racecar. Non-afterburning. But a racecar. It doesn't like to go slow :)

 

Either way, this doesn't belong in the bug report section. This isn't a bug. It's how it's supposed to be.

[FoxDelta]

Observed this too.

I dont think an A/C flying steady level will ever accelerate on IDLE.

Water was always off and flaps 05.

Had to put the nozzles down a few degrees to stay behind the tanker.

 

I do consider this as bug.

[Mars Exulte]

Idle in this case is 45% thrust. Show me one aircraft in clean profile, level flight, will not accelerate over 200kts at 45% power. There isn't one, except the A-10. Even the prop fighters are apt to exceed 200kts at 45% power.

 

The question is not 'should it exceed 200kts at 45% thrust'. The question is 'is 45% power really the idle setting'?

 

Based on the already mentioned warning regarding parking brakes and nozzles, I'm inclined to say YES. But if you really want to know, go to the NATOPS manual and see.

 

I repeat, not a bug that it accelerates over 200kts at 45% power. Increase the tanker speed and stop trying to refuel at a near stall.

 

For further food for thought bear in mind the Pegasus is a 25,000lb thrust engine. 45% power is around 12,000 of thrust, or one engine on an A-10 at full power on an aircraft considerably heavier than a Harrier.

 

Will 12,000lbs of thrust propel a 25,000lb Harrier (assuming clean config and full fuel) over 200kts? YES.

 

This isn't that hard.

Edited January 16, 2018 by zhukov032186

[TheThumper]

I have experienced the same. Throttle-Idle;Water-Off and still accelerating. I was toggling the speedbrake, but adjust the nozzles is much smarter idea. Hopefully they can reproduce and tune.