Ask The Pilot

[jb747]

This is the semi-official "Ask the Pilot about MS Flight Simulator" thread.
I see that FS2024 is now out. Do any of you folks play MS FS in any of its forms or is DCS the way to go?

DCS for sure! Growling Sidewinder.

 

[jb747]

Interesting MEL-SYD flight today 30/11 on QF426... Originally scheduled to depart at 0900 it was delayed to 1201 due weather in Sydney. We took off on RWY27. I was sitting in 4C and as we rotated I noticed a change in the pitch of the engines as they spool up. As well there was a very noticeable vibration throughout the aircraft. We entered into cloud at around 1,000 feet and continued to track west at low speed and a low rate of climb. We levelled off at around 8,000ft and continued to travel west and turned to the south and tracked towards Avalon then tracked to the east over Port Phillip Bay. The Captain came on the PA and said we had lost one of our primary instruments on take off and due weather in Sydney, Canberra, Melbourne and Hobart we would need to divert to Adelaide to conduct a visual approach. On landing in Adelaide and walking off the plane I noticed the Captains side Pitot Tube had detached from the side of the aircraft and was hanging in place.

4ºC is within the icing range, so that's what I'd expect as the cause of the vibration. If the engine had eaten something, I suspect it would have been unmistakable. The profile for the diversion is interesting. The aircraft is lower than you'd expect, and relatively slow for the entire journey. So, sounds like it was also non RVSM. Can't see any bird remains, so probably not a bird strike.

See attached.... Not sure if this was the result of a bird strike or something similar. I would have assumed that an alternative static source would be available on the 737's to provide airspeed to the tech crew. Why the necessity to divert to an airport (Adelaide) for a visual approach....

I'm sure there's a third source, but you can't just flick to that and then fly to a place with very poor weather if you have any other alternative. The best alternative is the diversion to a VFR airfield. If they hadn't been able to take that option, then you'd probably still be in Melbourne. Backups are to keep everyone alive, not necessarily to allow business as usual.

 

[ChrisGibbs]

Would all of the automatics have been available or would things have degraded- autothrottle, etc was the autopilot still available or would the workload have been significantly higher?

After takeoff and the initial cruise at 8,000 ft there felt to be an appreciable nose up attitude..Also the altitude appeared to be off by a 200ft or so. Not bang on 8,000ft but 8,200ft

 

[jb747]

Would all of the automatics have been available or would things have degraded- autothrottle, etc was the autopilot still available or would the workload have been significantly higher?

After takeoff and the initial cruise at 8,000 ft there felt to be an appreciable nose up attitude..Also the altitude appeared to be off by a 200ft or so. Not bang on 8,000ft but 8,200ft

We'll need AV for the exact details, but I'd expect the autothrottle to still work, though perhaps not in all modes. The right autopilot should have been available (does the 737 have a C?). Presumably the Captains source select would have been taken to the alternate. The altitude difference is probably explained by difference sources of data, though I'd have expected the ADSB and autopilot (flying pilot) to be using the same source. Let's see what AV has to say.

 

[ChrisGibbs]

The Captains PA specifically made mention the FO was flying the aircraft ‘perfectly’..

Would the Captain has felt / heard the Pitot Tube seperate from the airframe?

 

[jb747]

The Captains PA specifically made mention the FO was flying the aircraft ‘perfectly’..

Would the Captain has felt / heard the Pitot Tube seperate from the airframe?

Perhaps, though I wouldn't guarantee it. Airspeed disagreements have caused accidents in the past, and they're trained for a lot these days.

 

[AviatorInsight]

Would all of the automatics have been available or would things have degraded- autothrottle, etc was the autopilot still available or would the workload have been significantly higher?

After takeoff and the initial cruise at 8,000 ft there felt to be an appreciable nose up attitude..Also the altitude appeared to be off by a 200ft or so. Not bang on 8,000ft but 8,200ft

The Autopilot (B) for the FO would be available. There is only 2. But even with the Captain’s Pitot out, the autothrottle is not to be reengaged. The system goes pretty deep but basically the autothrottle is a function of the capt’s flight control computer.

The flight profile you experienced tells me the crew had an unreliable airspeed indication shortly after take off. The memory items call for a pitch attitude of 10° and 80% N1 with flap out. This keeps the aircraft flying within the flight envelope until a reliable source can be determined.

The tracking they flew looks like the engine out procedure for runway 27. Track straight ahead to 11nm then a left turn to track 180°.

With the Capt’s airspeed unreliable, the airspeed indicator acts as an altimeter. That is, the airspeed increases as the altitude increases. At some point the overspeed warning clacker will go off and continue to go off until you descend again.

As for the altitude difference being 8200ft and 29,100ft the ADSB readout comes from the transponder. We have 2 of those and so will select 1 or 2 depending on who is flying. It could be that the Capt was the PF so transponder 1 was selected but then transferred flying to the FO and autopilot B was in. This would mean the Autopilot was flying at exactly 8000ft on the FO’s side but the altitude readout would have been from the Capt’s side of the transponder.

They could have flown into RVSM airspace as the altimeter would still be functioning on both sides. The standby doesn’t count, but they were flying at hemispherical levels (even levels flying westbound).

The Captains PA specifically made mention the FO was flying the aircraft ‘perfectly’..

Would the Captain has felt / heard the Pitot Tube seperate from the airframe?

He may have heard it banging on the side, but wouldn’t have felt it. The 737 is quite noisy (around 80db), even with noise cancelling headsets there would be more going on inside to even notice that anything had snapped.

The necessity to divert to an airfield with visual conditions is probably not a bad idea. I’d be interested to see if they did a flap 15 or flap 30 landing. Because the Capt’s airspeed is what the flap load relief works off.

I literally had a sim about 6 weeks ago that concentrated on the Capt’s pitot becoming damaged out of CNS. Was a good exercise.

 

[jb747]

AV, does the 737 not have a third pitot source? Not the standby, but a selectable source for either of the pilots?

And is the MAX the same?

And this requirement should have been queried by ATC: "A secondary surveillance radar (SSR) transponder with altitude reporting synchronized with the altimeter".

 

[AviatorInsight]

AV, does the 737 not have a third pitot source? Not the standby, but a selectable source for either of the pilots?

And is the MAX the same?

And this requirement should have been queried by ATC: "A secondary surveillance radar (SSR) transponder with altitude reporting synchronized with the altimeter".

That’s correct. There is no 3rd source for the primary instruments. The Aux pitot on the FO’s side is for the standby and there are 2 elevator pitots on the fin for the elevator feel computer.

If all 3 airspeeds are unreliable we just need to fly the pitch and thrust we get from the QRH. Ground speed is still reliable so will give you a rough idea.

 

[jb747]

If all 3 airspeeds are unreliable we just need to fly the pitch and thrust we get from the QRH. Ground speed is still reliable so will give you a rough idea.

Airbus came up with a very neat system in the 380 called the “backup speed scale” or BUSS. When active, it replaces the speed scale on the PFDs. It’s angle of attack based, but is very easy to fly. It has migrated to the A350 and I presume is appearing in other new build ABs.

As an aside, in QF30 we ended up with a “single source select” warning, as both the left and right instruments had to be selected to the right source/ADC. Left and centre had both failed.

 

[Quickstatus]

When active, it replaces the speed scale on the PFDs

Does that mean that Stall warning is also switched off?

If all 3 airspeeds are unreliable

What other indicators/symptoms are there that all 3 are suspected to be unreliable but they are reading exactly the same?