Ask The Pilot

[jb747]

Why do you say that?

I see it as an excuse for inaction. While you can hold this up as a goal, you don't have to take the long overdue action to get a reasonable stream of aircraft replacements happening.

The range payload equation is appalling. Arrival fuel figures are very low, and will not handle weather or ATC delays. New York was difficult to manage when you were departing LAX. Fuel burn could vary enormously...and this will be even more of a problem for a longer flight.

Biggest issue of all though is that the entire premise is based up the passengers paying a substantial premium on their fare, in order to save an hour or two. Some will, but I expect most won't.

 

[Quickstatus]

If MCAS were to be redesigned what would the new features include?

1) limit extent of auto stabiliser trim
2) MCAS inactive if disagreement between the 2 AoA probes
3) Change the regulatory side by making the 737M8 a different aircraft to the 737-800, requiring pilot type certification on that aircraft.
What else?

 

[AviatorInsight]

If MCAS were to be redesigned what would the new features include?

1) limit extent of auto stabiliser trim
2) MCAS inactive if disagreement between the 2 AoA probes
3) Change the regulatory side by making the 737M8 a different aircraft to the 737-800, requiring pilot type certification on that aircraft.
What else?

Allow pilots to override the system with opposite trim and/or opposite elevator control.

 

[jb747]

If MCAS were to be redesigned what would the new features include?

1) limit extent of auto stabiliser trim
2) MCAS inactive if disagreement between the 2 AoA probes
3) Change the regulatory side by making the 737M8 a different aircraft to the 737-800, requiring pilot type certification on that aircraft.
What else?

1) Limiting the extent of it's ability to use the stab would very likely mean that it doesn't fulfill the 'anti-stall' reason that it was installed. So, yes, I'd limit it, but if that doesn't do what's needed, then I'd remove it entirely.
2) Fine idea, but there should be 3 probes.
3) The 737 has a basically archaic coughpit because of a desire to avoid type endorsements. Prior to the Max, the coughpit hadn't even reached the 767 (mid 80s era).

4)It should stop, and never restart, once there is pilot activity in the opposite direction, be it via trim or control column input.

Boeing have avoided the real fix, because they are entirely locked to the idea of not building a 737 replacement. Basically, the tail volume should be increased, so that normal flight control inputs allow the aircraft to pass the FAA test.

It's a pity they didn't simply put the 737 to rest, to do more with the 757. In the interim the A321 has pretty much morphed into a 757....

 

[Quickstatus]

But the unintended in 4) is the pilot who puts in an AF477 style input gets to override a correct MCAS. But then that’s the Boeing mode - the pilot has authority

Larger tail volume - meaning more rudder and elevator surface to compensate for stronger pitch moment of the larger engines?

 

[Must...Fly!]

It has been quite some time since I visited this thread (my fault...), but I thought this incident might be worthy of posting and may prompt some discussion. A little over the 737 MAX talk all over the internet today.

Incorrect configuration involving Airbus A330, Melbourne, Vic., on 2 December 2018

(I searched and couldn't find it being mentioned anywhere else).

 

[Quickstatus]

It has been quite some time since I visited this thread (my fault...), but I thought this incident might be worthy of posting and may prompt some discussion. A little over the 737 MAX talk all over the internet today.

Incorrect configuration involving Airbus A330, Melbourne, Vic., on 2 December 2018

(I searched and couldn't find it being mentioned anywhere else).

Normally this is an "Ask the Pilot" which usually requires a question for the pilots.
In any case this was MH128 MEL-KUL...

 

[jb747]

But the unintended in 4) is the pilot who puts in an AF477 style input gets to override a correct MCAS. But then that’s the Boeing mode - the pilot has authority

Any aircraft can be stalled, if you have a pilot who does not know what he's doing. A stall in itself shouldn't be all that much of a problem. Heck, in my military days we lived on the edge of them. The pilot from AF447 held full aft stick from altitude. That stick position has use for only a few seconds in most pilots' years...not minutes on one flight. The AB actually trimmed nose up, which made it worse, because it was attempting to relieve the nose up stick loading. Neither the trim nor the elevator were what was wanted. AB won't normally let you stall the aircraft, but it will accurately hold the maximum angle of attack. It uses elevator to do that, not trim. The logic of MCAS is deeply flawed.

Larger tail volume - meaning more rudder and elevator surface to compensate for stronger pitch moment of the larger engines?

Larger control surfaces, or longer moment arm.

 

[Must...Fly!]

Normally this is an "Ask the Pilot" which usually requires a question for the pilots.
In any case this was MH128 MEL-KUL...

Fair point, I apologise. And actually I believe it was an Air Asia X flight, before they moved off to AVV.

To ask a general question then - does the autopilot differ significantly between Boeing and Airbus aircraft? Is there a philosophy difference for AP between the manufacturers, or is it more dependent on type/modernity of the frame itself. Something I've never really thought about until today.

 

[jb747]

It has been quite some time since I visited this thread (my fault...), but I thought this incident might be worthy of posting and may prompt some discussion. A little over the 737 MAX talk all over the internet today.

Incorrect configuration involving Airbus A330, Melbourne, Vic., on 2 December 2018

Nothing about this is good.

Due to possible windshear, it was decided to use maximum take-off thrust1]. The crew reported a normal take-off.

Fair enough.

Passing 500 ft above mean sea level (AMSL), the captain engaged the autopilot and reduced the power to climb thrust.

Normal climb thrust engagement should be at 1,000'.

The climb rate of the aircraft then reduced and the aircraft levelled off around 760 ft AMSL. The crew, suspecting windshear, retracted the flaps and then set take-off/go around (TOGA)2] power.

Wow. How about 'open climb'? And retracted the flaps. Eek. In shear the configuration should not be changed. If they'd really been in shear, that would have made it much worse.

The overspeed was because the power was at TOGA....the auto thrust is not engaged in that mode.

Normally this is an "Ask the Pilot" which usually requires a question for the pilots.
In any case this was MH128 MEL-KUL...

Was it? I thought the discussion on pprune had it as being our old mates, Air Asia.

 

[jb747]

Fair point, I apologise. And actually I believe it was an Air Asia X flight, before they moved off to AVV.

It was.

To ask a general question then - does the autopilot differ significantly between Boeing and Airbus aircraft? Is there a philosophy difference for AP between the manufacturers, or is it more dependent on type/modernity of the frame itself. Something I've never really thought about until today.

Modes are functionally equivalent, but they do work sufficiently differently that it's best not to try to translate from one type to another. Open climb/descent is pretty much the same as FLCH. V/S is V/S. LNAV and NAV. VNAV and 'managed climb/descent'. Boeing has no equivalent to FPA (flight path angle).

Autothrust and autothrottle are very different....as is thrust management manually.

 

[flyer89]

Wow. How about 'open climb'? And retracted the flaps. Eek. In shear the configuration should not be changed. If they'd really been in shear, that would have made it much worse.

When I saw the part about the flap retraction I shuddered. They are the gift that keeps on giving until innocent people die (again).

 

[Quickstatus]

Was it? I thought the discussion on pprune had it as being our old mates, Air Asia.

Ah thanks
It’s D7 213.
I had incorrectly recalled that MH departed after D7 when both were operating out of Tullamarine)

The operator response should have been a giveaway - just do a few more sims.

Re flap retraction on that flight:
It seems that the flight crew wanted to fly faster . To generate more lift?. Higher speed less flap vs a little less speed and more flaps - which is better under those conditions?

 

[Must...Fly!]

Thanks jb - did not know it made it to pprune - I might go have a read. It's been years since I ventured there...

Flight Path Angle and V/S - the former keeps the aircraft on a set angle and flies accordingly to hit a specific altitude at a target point? And V/S just manages descent in fpm?

 

[jb747]

Re flap retraction on that flight:
It seems that the flight crew wanted to fly faster . To generate more lift?. Higher speed less flap vs a little less speed and more flaps - which is better under those conditions?

You give them too much credit. I don't think they had the slightest idea what they were doing. Flaps, especially at the levels they're used at take off, have very little drag, but they have an enormous effect upon the amount of lift, and also (depending upon whether you have slats or leading edge flaps) the available angle of attack. Retracting them is crazy.

 

[jb747]

Thanks jb - did not know it made it to pprune - I might go have a read. It's been years since I ventured there...

Just keep in mind that most people who post there are not pilots...!

Flight Path Angle and V/S - the former keeps the aircraft on a set angle and flies accordingly to hit a specific altitude at a target point? And V/S just manages descent in fpm?

V/S...vertical speed, is a set rate of climb or descent. It takes no account of speed, and will accelerate beyond what you want at one extreme, and run you into the stall warnings at the other. Normally only of use in the later half of a descent.

FPA...flight path angle. The aircraft will fly a geometric descent (or climb) angle. Useful for non coded, non precision approaches, where the angle is about 2.5-3.5º. No other use. A coded approach means that it's in the FMC, and can be flown using FAPP (yet another mode). It will not target any altitudes or points, simply that path.

 

[AviatorInsight]

Boeing has no equivalent to FPA (flight path angle).

Except in the 777.

I used it on many occasions conducting NPAs once I was on profile. Worked a treat!

 

[jb747]

Except in the 777.

I used it on many occasions conducting NPAs once I was on profile. Worked a treat!

Well, I'll stand corrected then. Not on any of the Boeings I've flown.

On the 380, we only ever used it in the sim. All of the non precision approaches that we might fly were coded, so we could us FAPP, in which case the aircraft built a simulated 3D GPS approach, and we flew it like an ILS.

 

[AviatorInsight]

Well, I'll stand corrected then. Not on any of the Boeings I've flown.

On the 380, we only ever used it in the sim. All of the non precision approaches that we might fly were coded, so we could us FAPP, in which case the aircraft built a simulated 3D GPS approach, and we flew it like an ILS.

Does that mean you got the chance to fly RNP approaches too? They are great to fly and the accuracy is unbelievable.

Interestingly enough the 777 only got approved about a month ago to fly RNPs and we had been doing them for years.

 

[Quickstatus]

Well, I'll stand corrected then. Not on any of the Boeings I've flown.

On the 380, we only ever used it in the sim. All of the non precision approaches that we might fly were coded, so we could us FAPP, in which case the aircraft built a simulated 3D GPS approach, and we flew it like an ILS.

Is this similar to what EK tried to do at JFK?