Ask The Pilot

[Quickstatus]

Engine driven hydraulic pumps. Generators. Mechanical fuel and oil pumps. That sort of thing.

Do these fuel pumps supply the engine combustors with pressurised fuel?

 

[jb747]

Do these fuel pumps supply the engine combustors with pressurised fuel?

Yes. If the mechanical fuel pump fails, the engine snuffs itself instantly, and cannot be restarted.

Do a search for this: cfm56 accessory gearbox

 

[Quickstatus]

cfm56 accessory gearbox

The way it is constructed, failure of any one of the gear driven pumps resulting in the jamming of the pump's spur gear could lead to the jamming and failure of the entire gearbox but evidently appear extremely reliable.

 

[jb747]

The way it is constructed, failure of any one of the gear driven pumps resulting in the jamming of the pump's spur gear could lead to the jamming and failure of the entire gearbox but evidently appear extremely reliable.

I have never heard of the failure of one of the spur gears. I think the drive shaft is the weak link in the design (probably by choice), and I've heard of them failing in all sorts of aircraft.

 

[Quickstatus]

Yes one failure leads to multiple loss of systems. Obviously rare unless both gearboxes /radial shafts get damaged

 

[jb747]

Yes one failure leads to multiple loss of systems. Obviously rare unless both gearboxes /radial shafts get damaged

Yes and no. Loss of the drive will kill the mechanical fuel pump, and you'll lose the engine. But, you'll be able to regain pneumatic, hydraulic and electrical services by starting the APU. Of course, if you've done something silly like landing on the engines, then all bets are off.

 

[mjt57]

Depending on the conditions, I would normally prefer to disengage the autothrottle (the 737 sucks at holding speed even with it in), so I like to kick it out early if it's gusty and just do it myself.

It was a clear and calm day.

Here's a photo that I prepared earlier of the aircraft in question:

 

[AviatorInsight]

It was a clear and calm day.

Here's a photo that I prepared earlier of the aircraft in question:

The only thing I can think of then, is that it’s manual throttle and the pilot flying is just chasing the speed rather than setting a power setting and flying the attitude.

On a calm day the auto throttle definitely won’t be moving that much to notice a change in engine noise from the ground.

 

[mjt57]

On a calm day the auto throttle definitely won’t be moving that much to notice a change in engine noise from the ground.

That is what made me curious. When in the aircraft and where I tend to be allowed to sit (despite me identifying as a first class pax) the engines usually sound fairly settled on approach.

 

[Major]

There is a balloon which has been flying over Australia for a couple of days Live Flight Tracker - Real-Time Flight Tracker Map | Flightradar24

Even though it's over 50,000 ft do you receive details in a NOTAM or other advice ?

 

[ChrisGibbs]

Do you recall anything different about the landing in Auckland? C hydraulic system out is a different landing configuration than normal.

I know its hard for a PAX to judge but I do recall thinking the approach speed seemed higher than normal and 'flatter' with the subsequent landing roll using the entire length of RWY23L. There was no significant feeling of braking or noise from reverse thrust. I couldn't see whether the slats / flaps had been extended and/or whether the speed brakes were deployed. We did have a couple of fire engines meet us at end the runway. They accompanied the aircraft as it was towed to a stand. Strangely there was no PA from the tech crew saying there was anything out of the ordinary.

The 'faster / flatter' approach and landing felt similar to one I experienced about 4-5 yrs back on a SIN-SYD QF2 A380 that had a flap extension asymmetric issue causing the flaps to lock in a certain position. We aborted the approach on RWY34L and spent about 15-20 minutes off the coast then made another approach onto RWY34L for what appeared to be a 'faster / flatter' approach.... Different to the Air NZ 767 scenario above the QF A380 reverse thrust was idle and braking seemed normal.... with the landing roll continuing on 34L until abeam Gate 8,9 at the international terminal. When the aircraft shutdown the Captain made a PA explaining 'what happened' back there.... On the way off the plane I exited out of the forward stairs. Not sure I picked up exactly what the Captain was saying to one of the crew - something like we had only recently done a Sim that covered this scenario....

 

[Aus ATC]

There is a balloon which has been flying over Australia for a couple of days Live Flight Tracker - Real-Time Flight Tracker Map | Flightradar24

Even though it's over 50,000 ft do you receive details in a NOTAM or other advice ?

It is one of many Google "Loon" balloons - for more information see Loon

No NOTAM but we (ATC) have arrangements to receive position reports and trajectory predictions every few hours from the Loon command centre. The balloons operate under an airways clearance when operating between FL500-FL600 (50000 - 60000 ft) and we are responsible for separation of other traffic from the balloon - usually vertically as few (if any) aircraft will fly above FL450. Above 60000ft- FL600 - the airspace is uncontrolled, but we still monitor the balloons progress. Fortunately we can mostly track the balloons using ADS-B.

The balloons will also be "cut down" at the end of their mission. That descent is coordinated with the ATC unit as well, and again we will separate the descending balloon from other traffic.

 

[jb747]

I know its hard for a PAX to judge but I do recall thinking the approach speed seemed higher than normal and 'flatter' with the subsequent landing roll using the entire length of RWY23L. There was no significant feeling of braking or noise from reverse thrust. I couldn't see whether the slats / flaps had been extended and/or whether the speed brakes were deployed. We did have a couple of fire engines meet us at end the runway. They accompanied the aircraft as it was towed to a stand. Strangely there was no PA from the tech crew saying there was anything out of the ordinary.

There are no approaches that are flown 'flatter'. They may seem that way because of a different body angle, and power setting, but they'll all be down the usual 3.0º slope.

Loss of C hydraulics means that the flaps will have to be extended via the alternate (and much slower) system. The approach will be flown at flap 20 (vs the usual 30). Speed will be about 10-15 knots faster. This approach requires appreciably less power, and it can be difficult to accurately control the speed as you don't have as much drag as usual. The landing gear will also need an alternate extension, and it cannot be retracted. Gear doors don't close after extension.

Reverse thrust operates normally, as do the aircraft brakes. Nose gear steering is not available.

The higher approach speed (and flap 20) is used to maintain adequate pitch control. You've lost one of the systems that operates the elevator; going faster offsets that somewhat. The aircraft is very prone to floating off this approach.

Automatic ground spoilers are not used, and they will be raised manually after landing. The spoilers are split across all of the hydraulic systems, and loss of the C system means that some are unpowered. This tends to give a pitch up on automatic extension.

The 'faster / flatter' approach and landing felt similar to one I experienced about 4-5 yrs back on a SIN-SYD QF2 A380 that had a flap extension asymmetric issue causing the flaps to lock in a certain position. We aborted the approach on RWY34L and spent about 15-20 minutes off the coast then made another approach onto RWY34L for what appeared to be a 'faster / flatter' approach.... Different to the Air NZ 767 scenario above the QF A380 reverse thrust was idle and braking seemed normal.... with the landing roll continuing on 34L until abeam Gate 8,9 at the international terminal. When the aircraft shutdown the Captain made a PA explaining 'what happened' back there....

The A380 has an enormous wing. It really surprised me when I first went to it, just how benign it was with flap malfunctions, right up to zero slat/flap landings. Approach speeds, even after a lock out, are similar to the normal speeds on a 747.

Asymmetric lock out will happen during flap motion. The chances are that it won't happen until you already have quite some flap out. It has no effect on other systems.

 

[RooFlyer]

Not too many. Basically anywhere we don’t overnight, so CFS, AYQ, BNK, HTI, PPP, ROK, ISA.

And HBA! I can say, from bitter ("Flight delay at least 3 hours - we have to fly engineer in from Melbourne") experience!

 

[AviatorInsight]

And HBA! I can say, from bitter ("Flight delay at least 3 hours - we have to fly engineer in from Melbourne") experience!

Flown in from MEL?? Did they tell you of the issue?

There is an engineer in HBA and LST as well to handle the overnights. The thing is, they’re on call at any other time. So it could take a while to call them out for a flight during the day.

 

[RooFlyer]

Flown in from MEL?? Did they tell you of the issue?

There is an engineer in HBA and LST as well to handle the overnights. The thing is, they’re on call at any other time. So it could take a while to call them out for a flight during the day.

Ooops ... my apologies. It was 'the other mob'; two days in a row the 6am departure HBA for SYD was delayed due to a fault and an engineer had to be flown in from Melbourne. The first time we taxied but, then returned. Second time we didn't get close. So, a question: Does VA and QF ever share engineering services at the smaller, or any port (at least where the same aircraft are involved)? Parts?

 

[jb747]

It was 'the other mob'.

It probably wasn't them either. It would have been the other, other mob. QLink is a totally separate entity to mainline.

 

[RooFlyer]

It probably wasn't them either. It would have been the other, other mob. QLink is a totally separate entity to mainline.

Does QantasLink have its own engineering services group? (Real question) And would they share regional services with VA, do you think?

 

[AviatorInsight]

Ooops ... my apologies. It was 'the other mob'; two days in a row the 6am departure HBA for SYD was delayed due to a fault and an engineer had to be flown in from Melbourne. The first time we taxied but, then returned. Second time we didn't get close. So, a question: Does VA and QF ever share engineering services at the smaller, or any port (at least where the same aircraft are involved)? Parts?

Engineering services? No they don't. Different sets of rules and procedures.

But we can use equipment if required. AYQ is a very common place where things break down (I have no idea why?), so we can use the QF ground start equipment if required, but because it's so expensive, network operations won't plan aircraft to operate to AYQ with an APU unserviceable. So if you need an engineer, they'll likely need to fly one in.

 

[27mrpc27]

Your idea of a good landing, and mine, are quite different.

Basically, for a passenger (or cabin crew), the only factor that they use is the 'smoothness' of the landing. Fair enough given that's the only factor that they can actually see (or feel).

Within the coughpit, that's almost the last thing we grade it on.

As a generalisation, really smooth landings are done by extending the flare into a longer 'hold off'. That increases the risk of tail scrape, lengthens the overall landing distance, makes handling any crosswind much more difficult, and increases the likelihood of aquaplaning on a wet runway.

Some aircraft are also quite prone to sitting down pretty firmly. The 767 was renowned for firm arrivals, even though everything should have led to a smooth touchdown. The general theory for that related to the way the gear translated during the landing, and the spoiler actuation.

The are limits beyond which maintenance action is required. For the 747 and 767 there were two figures. 1.4 and 1.8g. Basically at the lower figure, a very quick look was all that was required, whilst the higher one required a visit to the hangar. The vast majority of landings, even ones you consider firm, are under 1.1g.

Answered just as I would have expected. Thanks for the insight.

Post automatically merged: Jun 2, 2020

I am happy to let the airline guys elaborate some more but you have touched upon a bit of truth. Suffice to say that a good or bad landing for a pilot can be substantially different to a passenger's perception of a good or bad landing.

Agreed. I am sure what we feel as pax and what is actually occurring with the aircraft are vastly different.