Video - landing with all engines shutdown

[andrej]

Hello all,

new video from a FFS of landing with all engines shutdown:

https://www.youtube.com/watch?v=RaYK1NCK_0Y

I was not expecting the end.

Cheers,
Andrej

[John H Watson]

The APU was already running in this video. I thought you couldn't start the APU in flight, but you can in the current version of PSX with no circuit breakers pulled.

The Primary Air Ground System should still be powered by the Battery Busses, so the aircraft should still be in air mode controlling air/ground relay R263 and R359. This will stop the APU inlet door opening. No door open, no start.

Has something changed in PSX?

[Hardy Heinlin]

I thought you couldn't start the APU in flight, but you can in the current version of PSX with no circuit breakers pulled.

I can't start the APU in flight in PSX when all CBs are in. How was it possible in your situation?
I can start when P7 F22 is pulled which will set an on-ground signal.

[ASCTU744]

These are the questions I asked him:

How was the APU started with all engines on and all AC busses pwrd?

Was the APU used to pwr the grd serv bus in turn powering the batt's?

And did the APU provide bleed air for the DEM pumps (I assume all 4 air driven), if so why did the pneumatic LE's not extend and the gear and TE flaps extend so slowly (with full HYD capability, EDP's and demand pumps)?

Why weren't the APU gens turned on?

Why did you lose hydraulic power on the ground with the demand pumps?

And why does the brake source light flicker?

It was a lufthansa sim btw

[Hardy Heinlin]

1.Why weren't the APU gens turned on?
2. Why did you lose hydraulic power on the ground with the demand pumps?
3. And why does the brake source light flicker?

1. APU GENs are never available in flight, even when the APU is running in flight. And even if they are ON on the ground, they'll reset to AVAIL when the thrust is out of idle.

2. I guess their APU didn't provide anything: No air, no hyd, no elec.

3. I guess it was about to lose the source power.

With the remaining accumulated brake power he can steer a little bit with the brake pedals, i.e. with controlled brake power asymmetry. But every toe brake movement will discharge the accumulator a bit. I guess at the end he had no reserves anymore. That was a long rollout from over 200 knots.


P.S.: In the video you see, when the AC power is lost, the brake pressure steam guage is no longer illuminated and the needle goes to 0 psi. But note that the actual pressure is not at 0 psi yet; the needle just turns to 0 because the indication system has lost its electric power.

[Andrea1]

Hi to all,
Another thing I can't understand about that video:
it's seems to remember that they said that approach was made at a speed of 250 (I assume knots) to windmill enough for having hydraulic pressure but..flaps are set at 20 and according with my B744 1.3 manual (I'm not with psx running now) max limits flaps speed are: flaps 1= 280 kts, flaps 5= 260 kts, flaps= 10= 240 kts, flaps 20=230, flaps 25=205, flaps 30= 180 kts..Are they overpass the limit for safety reasons (for having enough hydraulic pressure)?

Best Regards
Andrea Buono

[Andrea1]

Ah ok..I've seen that flaps have never reached the selected 20 degrees position...

[John H Watson]

I can't start the APU in flight in PSX when all CBs are in. How was it possible in your situation?

I used the Basic 020 scenario (idle descent to 10000'). I shut off all 4 engines, then after all four generators went offline, I started the APU. Both APU gens showed available. I only selected APU #1. All my power returned.

[Hardy Heinlin]

Ah, OK. It works when all engines are shutdown. I forgot that I modified it many years ago. I think it refers to observations on KLM/Lufthansa sims and according to that, PSX models it correctly. No?

[John H Watson]

I forgot that I modified it many years ago. I think it refers to observations on KLM/Lufthansa sims and according to that, PSX models it correctly. No?

I may have overlooked something. With the Battery busses powered, the Primary Air/Ground System is still operative. The APU inlet door control circuits are controlled by the Primary Air Ground System relays R263 and R359. However, relay R263 is powered by DC Bus 1 (which isn't powered in this scenario), so it defaults to GND mode. This energises relay R359 allowing the door to open.

I assume if you try to put APU power on, it will energise Bus 1, but the door may simply run to its narrower flight position (not close).

[Hardy Heinlin]

Just found the mod log (PSX update 10.0.3 from February 2015):
https://aerowinx.com/board/index.php/topic,2637.0.html

Beta 3:
0.3-0007. Bug cleared: APB trip signals in certain inflight conditions were sent but not received. Pushing any APB switch from AVAIL to ON under all eng/out conditions now removes AVAIL status from other APB (as observed in KLM sim).

Here's the initial discussion (Feb 2015):
https://aerowinx.com/board/index.php/topic,2620.0.html

[John H Watson]

2. I guess their APU didn't provide anything: No air, no hyd, no elec.

I forgot about APU Bleed. You can get bleed air from the APU in the air. The ADPs would run with APU bleed, so they should have had hydraulics for brakes and steering ().

Did the aircraft veer off the runway because of other reasons? Blown tyres?

Here's the initial discussion (Feb 2015):
https://aerowinx.com/board/index.php/topic,2620.0.html

Now I remember. CB H8 is powered by DC Bus 1.

[Hardy Heinlin]

You can get bleed air from the APU in the air.

Yes, sufficient for 1 pack up to FL200, I think. But in the video it seems the LE flaps aren't moving. Maybe they have all 3 packs on?

Edit:
In PSX, the number of available packs on pure APU bleed air depends on the pressure altitude: Zero packs above FL200, three at circa FL100. Also, the limited bleed air from the APU has a certain priority: When the LE flaps move, the packs are off. I guess this makes sense. The flaps are more important than the packs being off for just a few seconds during flap motion.