Ask The Pilot

[jb747]

There is an interesting article in today's New York Times about pretty much that. The claim is that they found that they had 40 seconds to diagnose and correct the problem. And - "The software, as originally designed and explained, left little room for error. Those involved in the testing hadn’t fully understood just how powerful the system was until they flew the plane on a 737 Max simulator, according to the two people."

So, 40 seconds, if you're a Boeing test pilot, know about the system, and also know that it's about to be triggered.

I find it hard to believe that any pilots were ever involved in 'testing' of this system. Most of us start to twitch as soon as trim is mentioned. We're all aware that trim is more powerful than the elevators.

Short time windows can exist for many situations, but they are the ones that are practiced, over and over.

 

[juliusg]

My question is this: would the A330-200 have the legs to do Brisbane - LAX and return? That would fix VA's fleet problem with 5 x 777. They really should have added ship # 6 to get a more consistent timetable instead of the loopy Brisbane timings they currently have. Then they could run a pair of A330 on LAX.

 

[lastrow]

In an article I recently read two factors caught my eye. One was that trim wheels are ancient and are no longer fitted to the B777 or B787, and the second was that the control column is made harder to pull back than to push forward. Apparently on at least one 737Max flight the pilots were able to (after killing the trim tab switches) maintain trim using the wheel and thus avert another tragic incident. Do you regard the elimination of the Trim wheel as an undesirable safety compromise?.

 

[Himeno]

My question is this: would the A330-200 have the legs to do Brisbane - LAX and return? That would fix VA's fleet problem with 5 x 777. They really should have added ship # 6 to get a more consistent timetable instead of the loopy Brisbane timings they currently have. Then they could run a pair of A330 on LAX.

Qantas used to run A330-200s on AKL-LAX. BNE-LAX is 570nm longer then AKL-LAX, but is within the quoted range of the A330-200 using the Airbus basic fitout.
332 on BNE-LAX would be technically doable, but would come down to wind conditions and the precise weight and load of the given frames used (eg, the VA A330s have 20J255Y, the airbus numbers are based on 36J210Y)

 

[jb747]

My question is this: would the A330-200 have the legs to do Brisbane - LAX and return? That would fix VA's fleet problem with 5 x 777. They really should have added ship # 6 to get a more consistent timetable instead of the loopy Brisbane timings they currently have. Then they could run a pair of A330 on LAX.

I expect that it could get there, but not back.

Qantas used to run A330-200s on AKL-LAX. BNE-LAX is 570nm longer then AKL-LAX, but is within the quoted range of the A330-200 using the Airbus basic fitout.

A manufacturer's range chart normally has very little relationship with the real world, especially when you start adding weather, ETOPs and the various other requirements into the the mix. They can obviously do it from NZ or Fiji...but that's quite a way further east. I'd expect that if it had been viable, QF would have tried it.

All aircraft are not created equal. Everything is an option. I'd expect that the Virgin aircraft were outfitted for the flights they had in mind, so fuel tank capacity, maximum weight, engine power and type, would have all been tailored to fit. I'm sure that AB could build you a 330 for the job, most likely an NEO.

 

[jb747]

In an article I recently read two factors caught my eye. One was that trim wheels are ancient and are no longer fitted to the B777 or B787

They aren't fitted to the Airbus, B747-4/800, B757, B767. There is another way of moving the trim with alternate trim switches in all of these aircraft. Trim wheels are ancient and have no place in a modern design.

....and the second was that the control column is made harder to pull back than to push forward.

I've never noticed that in anything that I've flown.

Apparently on at least one 737Max flight the pilots were able to (after killing the trim tab switches) maintain trim using the wheel and thus avert another tragic incident. Do you regard the elimination of the Trim wheel as an undesirable safety compromise?.

Using the trim wheel did not avert the accident. Turning off the stab switches did. MCAS is the undesirable compromise.

 

[RailFlyer]

I think it has been mentioned recently, that to engage Auto pilot you have to have the aircraft in trim and no control inputs. As such, when taking off on a bumpy day (i.e. with lots of turbulence and seat belt sign stays on longer than normal) is it possible to easily get to a zero control inputs state and engage auto pilot soon after take off, or are the pilots hand flying until things get stable?

Likewise in the cruise when we hit turbulence big enough for a the seat belt sign to be put on, is the auto pilot always left to fly the plane or do the pilots hand fly in really bumpy conditions.

I think I might have said it here before, but my mild fear when flying in turbulence would be cured if there was a camera feed of the coughpit so I can see if the pilots look calm or if they are having to wrestle the controls, sweating etc. I expect 99% of the time they are total calm and it is just business as usual, but down the back it can be easy to start imagining that they are just holding onto the thing by sheer luck (Note: I fly into Wellington a lot!)

 

[jb747]

I think it has been mentioned recently, that to engage Auto pilot you have to have the aircraft in trim and no control inputs. As such, when taking off on a bumpy day (i.e. with lots of turbulence and seat belt sign stays on longer than normal) is it possible to easily get to a zero control inputs state and engage auto pilot soon after take off, or are the pilots hand flying until things get stable?

No problem at all. If there’s lots of pushing and pulling going on, then you’re almost certainly overcontrolling, and best to actually let go for a second. That’s how we test for ‘in trim’.....

Likewise in the cruise when we hit turbulence big enough for a the seat belt sign to be put on, is the auto pilot always left to fly the plane or do the pilots hand fly in really bumpy conditions.

Mostly when the signs go on, it’s because we’re in close proximity to radar returns that indicate that it might be turbulent. The autopilot is always left on. Older autopilots even had ‘turbulence’ modes, in which their parameters were relaxed a little, but modern ones (i.e. the last 30 years) don’t need a TURB mode, and are quite capable in their normal operating modes.

I think I might have said it here before, but my mild fear when flying in turbulence would be cured if there was a camera feed of the coughpit so I can see if the pilots look calm or if they are having to wrestle the controls, sweating etc. I expect 99% of the time they are total calm and it is just business as usual, but down the back it can be easy to start imagining that they are just holding onto the thing by sheer luck (Note: I fly into Wellington a lot!)

I’ve said before that I am totally against any form of camera feed from the coughpit, and if fitted it would have given me a place to hang my hat. You would be seeing stuff that you have no concept of, or ability to interpret. How would you react to (say), a Master Caution, and ECAM in the middle of the night?

The most annoying thing about turbulence, from the pilots point of view is that a) it may spill any coffee that we already have, and b) it stops us getting a coffee if we don’t already have one.

If you are flying with ‘sheer luck’ airlines, then it’s time to choose another. Wellington can be interesting, but it is specifically trained for. The fact that there’s a good safety record there, despite the well known winds, would suggest that the training works.

Turbulence....there is NO SUCH THING as an ‘air pocket’. Aircraft do not drop thousands of feet in turbulence encounters. In very extreme cases, it might be measured in feet. Most are literally inches.

 

[por930]

I am curious about the 787-9 that flies the Perth-London non stop route. I realise you may not be very familiar with the 787-9 aircraft but wondered if Qantas had a 'special' long range type or simply reduced cargo, managed pax levels, used a lower index and other 'fuel' saving methods to achieve the non stop flight. I guess the Boeing published payload range graph provides lots of scope for the various aircraft owners?

 

[jb747]

I am curious about the 787-9 that flies the Perth-London non stop route. I realise you may not be very familiar with the 787-9 aircraft but wondered if Qantas had a 'special' long range type or simply reduced cargo, managed pax levels, used a lower index and other 'fuel' saving methods to achieve the non stop flight. I guess the Boeing published payload range graph provides lots of scope for the various aircraft owners?

There’s nothing special about them. The 787 was designed with long, thin, routes in mind. Max passenger load is quite low, at 235 or so. The route is pretty well the maximum the aircraft can achieve.

 

[woodborer]

I’ve said before that I am totally against any form of camera feed from the coughpit, and if fitted it would have given me a place to hang my hat. You would be seeing stuff that you have no concept of, or ability to interpret. How would you react to (say), a Master Caution, and ECAM in the middle of the night?

I can't imagine that many people would be happy with the public being able to scrutinise their every move. See enough of baggage handlers just doing their job and people complaining that they aren't handling their cases with cotton wool....

 

[WheelieBagWanderer]

Hi There Pilots,

Regarding the Jetstar Osaka flight last week...

I would assume it's unlikely to have two engine problems on approach and my initial thought was contaminated fuel, but apparently that's being close to ruled out (according to this article anyway).

FR24 shows it flew to AKL on a non-scheduled flight and spent a couple of days there prior to flying to CNS and KIX.

Regardless of the actual cause, what exactly is an "engine surge" and how common is it? What is the procedure for dealing with it on the flight deck?

https://www.smh.com.au/business/com...s-minutes-before-landing-20190403-p51abg.html

 

[jb747]

Hi There Pilots,

Regarding the Jetstar Osaka flight last week...

I would assume it's unlikely to have two engine problems on approach and my initial thought was contaminated fuel, but apparently that's being close to ruled out (according to this article anyway).

FR24 shows it flew to AKL on a non-scheduled flight and spent a couple of days there prior to flying to CNS and KIX.

Regardless of the actual cause, what exactly is an "engine surge" and how common is it? What is the procedure for dealing with it on the flight deck?

https://www.smh.com.au/business/com...s-minutes-before-landing-20190403-p51abg.html

My knowledge of the 787 is quite limited (though I can ask some friends flying it for specific information if needed). The chances of a double, unrelated, problem are extremely limited. But, there have been some odd 787 failures. A Japanese aircraft experienced a double shutdown on landing recently, apparently when reverse was selected, then quickly cancelled. As that was a pretty common activity, the outcome would have to be considered surprising!

Engine surging (often, and confusing for the media, also called engine stalling), is basically the jet aircraft equivalent of a backfire. Looked at simply, air flows into the front of a jet, goes through a series of compression stages, gets to the combustion stage, and is then exhausted through another series of turbine stages. Any interruption to the flow, or breakdown in its dynamics can cause uneven combustion, with pressure surging out of the front, or bursts of flame out of the rear. An engine that is surging is not producing viable thrust, will be making horrid banging (or popping) noises, and because the flow through the combustion cans is no longer properly controlled, will often have massive temperature increases.

Stalling is not a normal event in modern engines. Some engines are prone to surging when starting, and sometimes selection of reverse upsets the flow enough to start an engine surging. In the start case, you shut the engine down, and restart it (as long as the temperature remained within limits). The giveaway to a start stall is a much more rapid than usual temperature rise. If an engine stalls in reverse, you simply take it back to forward idle, and in 99% of cases, that clears the stall.

Surging at high power is almost always the result of blade damage. Whilst you’ll try to clear the stall by taking the thrust back to idle, you’ll most likely need to actually shut it down to stop the temperature rising.

Most passenger reports of engine fires are actually stalls. Whilst certainly not desirable, you have to remember that jet engines are always on fire (when running), it’s just that you normally can’t stick your head up the exhaust to see. An engine fire, is something that happens outside of the hot areas of the engines.

 

[lastrow]

If an engine stalls in reverse, you simply take it back to forward idle, and in 99% of cases, that clears the stall

If you are hurtling down the runway after touch down and you select reverse thrust to slow up, the last thing you would want is an engine stall. Having just landed would you have time to take it back to forward idle with a view to re using it if the stall clears, or would you just leave it in idle and take the other one back to idle as well (assuming one engine on each side) and apply a bit heavier braking. I guess that one engine alone operating in reverse thrust would cause enough asymmetry to cause steering difficulties.

 

[AviatorInsight]

If you are hurtling down the runway after touch down and you select reverse thrust to slow up, the last thing you would want is an engine stall. Having just landed would you have time to take it back to forward idle with a view to re using it if the stall clears, or would you just leave it in idle and take the other one back to idle as well (assuming one engine on each side) and apply a bit heavier braking. I guess that one engine alone operating in reverse thrust would cause enough asymmetry to cause steering difficulties.

Reverse thrust doesn’t have much braking effect at all. The brakes do most of it while the spoilers help to maximise that effect by dumping the lift and putting the weight on the wheels. Steering is done through the rudder until about 40kts. No real difficulties at all.

We’ve had to lockout a thrust reverser on one side before and the increase in landing distance was about 50m.

 

[jb747]

If you are hurtling down the runway after touch down and you select reverse thrust to slow up, the last thing you would want is an engine stall.

Actually there are many things much worse than an engine stall.

You're obviously a somewhat nervous flyer (as is a very large percentage of the public). I expect you'll find the pilots are somewhat more relaxed.

Having just landed would you have time to take it back to forward idle with a view to re using it if the stall clears, or would you just leave it in idle and take the other one back to idle as well (assuming one engine on each side) and apply a bit heavier braking. I guess that one engine alone operating in reverse thrust would cause enough asymmetry to cause steering difficulties.

Reverse thrust is quite a misnomer. There is precious little actual reverse thrust generated. An engine capable of 60,000 lbs of forward thrust might generate as little as 3,000 lbs of reverse. When you select reverse, the fan cowling moves forward, and a series of blocker doors close the normal fan flow rearwards, and instead direct it sideways out of the engine. The might be a component forward, but it's not a great deal. At the same time, the core of the engine (the hot section) is continuing to push its exhaust to the rear as usual. So, you now have the situation of the fan section flow being blown mostly sideways, whilst the core is still pushing to the rear. As the core of a large engine might be providing 10,000 lbs of thrust, it serves to cancel out most of the effect of reverse from the fan. But, if the engine were simply at idle, you'd still have idle forward thrust, versus the neutral to slightly negative outcome with reverse.

That sideways blasting effect also helps remove water from wet runways.

Once you take an engine out of reverse, you don't put it back in.

Thrust asymmetry in reverse thrust is easily handled. So easily that you can operate the other reversers when you have one locked out (by MEL).

Braking is handled in a number of ways. On most landings you'll have some level of automatic braking selected. That targets a deceleration rate, so the braking will automatically vary with application of reverse. BTV (brake to vacate) takes that a step further, using GPS to target a selected taxiway exit point. And if you get really bored, you can do it yourself.

 

[jb747]

Stall...a simple word, so often misunderstood.

An aerodynamic stall occurs when the aircraft angle of attack (basically the angle between the wings and the actual flow) reaches a critical angle, and the airflow breaks away from the wing. It is such a basic part of aviation that it appears in the first couple of flights for any new pilot. You can feel it coming, mostly in the form of vibration (judder). Manually flying right on the edge of the stall was something that fighter pilots spent a fair bit of time doing. If you go a little too far, you simply release the back stick and the aircraft recovers pretty well instantly.

Stalling has absolutely nothing to do with your attitude. The papers have been saying that the 737 MCAS comes in to play if the nose 'gets too high'. No. It comes in to effect if the angle of attack gets too high. Attitude and angle of attack are two different animals.

Most stalls that occur accidentally aren't the result of pulling too hard, but happen because pilots have accidentally slowed down too much....and that's how most basic pilot training looks at the stall. Take the power to idle in level flight. Try to hold level, by pulling more and more back stick, and eventually you'll reach that magic AoA. The recovery isn't instant as it is in the previous case, as the engine(s) will take time to accelerate, and you'll need to trade of some level of height for speed.

An engine stall, we discussed above...

 

[Captain Halliday]

When you’re notified pre-flight of a MEL item, do you do anything on the flight deck to make sure you don’t inadvertently try to use the MEL item in times of high workload?

I ask because on a BA flight this week (A319) the attitude indicator had a post-it note over it saying IN-OP. It looked a little funny in a high-tech flight deck. But I guess simple solutions are sometimes the best.

 

[jb747]

When you’re notified pre-flight of a MEL item, do you do anything on the flight deck to make sure you don’t inadvertently try to use the MEL item in times of high workload?

I ask because on a BA flight this week (A319) the attitude indicator had a post-it note over it saying IN-OP. It looked a little funny in a high-tech flight deck. But I guess simple solutions are sometimes the best.

Those little stickers, are themselves part of the MEL. It may have a requirement that an item be marked with a particular type of label.

We used to print out any procedures that an MEL threw up. The idea was always to slow down, to ensure you were on top of the workload...if you aren't, then you're doing something wrong. That's one reason why application of MELs almost always delays every flight until the MEL is removed.

 

[eric2011]

In the aviation world, do you use true north or magnetic