Ask The Pilot

[jb747]

Why not?. Customary?
Altitude above field elevation of zero sounds more logical unless there are other reasons for QNH

Firstly, it's simply the rule in most countries. Russia is an exception, using QFE below 5000.

It does have it's uses. For instance, if you're doing aerobatic display flying, half way through a loop isn't the time to be trying to add airfield elevation to get your entry gate.

But, it causes issues with separation, as you'll need to work out how you're going to keep aircraft that aren't coming to a particular airport separate from ones going somewhere else, or in a go around. Local hills are also an issue, as you'll need your charts to give the terrain height differently for each local airport. It would be a nightmare at places like LA, where you have local very high terrain, and multiple airports, all at different elevations. Imagine a go around, where you need to fly QFE for the approach, QNH for the go around, and then back to QFE. All at low level, in a busy environment.

 

[Saab34]

Do you stay on top of that yellow taxiway line? I have flown some carriers on the video cam, they seem to keep the wheel a tad to the right or left. I assume to avoid the vibration of taxiway lighting?

 

[jb747]

Do you stay on top of that yellow taxiway line? I have flown some carriers on the video cam, they seem to keep the wheel a tad to the right or left. I assume to avoid the vibration of taxiway lighting?

On the 767, 747 and 380, there was more than enough space between the front wheels for you to straddle the centreline and yet still miss the lighting. Even during the take off roll. Well most the time, anyway.

If you taxi off the centreline, how far do you go? One metre. Two. That's space that's coming out of your wingtip, and main gear clearance. Clipping an object, would not be a good look, any yet not staying on the centreline makes that sort of error more likely. You don't have to go far off either, before you start running over lights with the body gear, so it's quite self defeating.

It's one of those little things in aviation, that's drilled in from day one (by the RAAF anyway). You aim at the centreline. Not near it. On it. It's the same with things like the circuit altitude. It's not nearly 1,000'. It's exactly 1,000'. If you aren't right on it, you should be correcting to get there. The idea is for that sort of accuracy to become natural and instinctive. And once it does, it drives you nuts when people are too lazy to do it!

 

[flyer89]

The idea is for that sort of accuracy to become natural and instinctive. And once it does, it drives you nuts when people are too lazy to do it!

I remember being reprimanded for having ‘lazy feet’ in the earlier days of my training. As time went by I came to understand that the old boy next to me might have a point.

 

[jb747]

I remember being reprimanded for having ‘lazy feet’ in the earlier days of my training. As time went by I came to understand that the old boy next to me might have a point.

You weren't keeping it in balance....?

 

[flyer89]

You weren't keeping it in balance....?

I was not. Lucky not to be struck over the head with a fuel drain for my misdemeanor.

 

[jb747]

I was not. Lucky not to be struck over the head with a fuel drain for my misdemeanor.

You've have loved engine out in the 767.

 

[Saab34]

Two engines out in one side in the A380, will it correct itself or are you holding heavy aileron to hold it in balance?

 

[jb747]

Two engines out in one side in the A380, will it correct itself or are you holding heavy aileron to hold it in balance?

Rudder. Lots of rudder. The system does try to help, 'cos it doesn't like sideslip, but you still need to do about 80% of the work.

Obviously, because it's by far harder, almost all practice of two engines out, involved them both being on the same side. But, they once had a bit of a fit, and gave us a cyclic with two symmetrically out. The amount of performance that we suddenly had was quite amazing. That huge rudder, keeping it straight, also gives masses of drag.

 

[Saab34]

Do you need to reduce speed with such heavy rudder in use? Ie-a danger it could fall apart due to stress?

 

[jb747]

Do you need to reduce speed with such heavy rudder in use? Ie-a danger it could fall apart due to stress?

As long as you don't do anything silly, like cycling the rudder from stop to stop, you won't break anything. The only time you'll need full (or almost full) rudder is at low speed (I think the worst case we used to hit was a go around off a two engined approach). As the aircraft accelerates, you'll be able to reduce the rudder substantially. You need to be careful with your speed management, because it's quite possible to run out of power, especially in hot conditions, so keep it clean and bit above green dot until you're into the approach was the normal way of managing things.

The idea during the approach was to keep the thrust lever movement to a minimum. 42% power rings a bell. The autothrust could stay engaged until around 1,000'. You'd approach the glideslope at flap 1, selecting the gear exactly 120 seconds before hitting the slope (because that's how long an alternate extension takes). As you hit the slope, flap 2. At 1,000' flap 3, and back to manual thrust. A 500' you're committed, and cannot go around (though it may well have happened much earlier). At 500' reduce the speed to Vapp, which may be below Vmca2.

I'll see if I can get the procedure to cut and paste to here....

 

[jb747]

LAND ANSA

● Depending on the failed engines:
PACK 1(2) .................................................................................................................................OFF

LDG PERF AFFECTED

● If ENG 1+2 failed and PRIM 3 failed or if ENG 3+4 failed and PRIM 2 failed: FUEL CONSUMPT INCRSD
FMS PRED UNRELIABLE

In the case of failure that increases the fuel consumption, the FMS predictions are not correct. If one outer aileron or one pair of outer ailerons is lost and partially deflected upward, fuel consumption may increase by up to 10 %.

● If ENG 1+2 failed:
FOR TAXI : STEER ENDURANCE LIMITED
The normal Nose Wheel Steering (NWS) is lost. ALTN NWS is available.
The ALTN NWS is designed to be used until the runway is cleared (i.e. to land and to exit the runway). Therefore, the flight crew should anticipate a tug to tow the aircraft back to the gate.
The flight crew should avoid a prolonged use of the ALTN NWS because it would result in: - An ALTNNWS overheat and the associated ECAM alert followed by
- A disconnection of the NWS.

In alternate nose wheel steering:

- The maximum steering rate is limited to 10°/s (instead of 15°/s for normal NWS)
- Damping of the CAPT and the F/O tillers is increased to prevent the flight crew from commanding excessive steering rates.


SECONDARY FAILURES

* ELEC
* F/CTL
* BLEED
* HYD

And then there's a few pages of STATUS messages....


LIMITATIONS ON ECAM

ALL PHASES
LAND ANSA
● If ENG 1+2 failed and PRIM 3 failed or if ENG 3+4 failed and PRIM 2 failed: FUEL CONSUMPT INCRSD

APPR & LDG

MAX SPEED : 220 KT
FOR LDG: FLAP LVR 3

● If ENG 1+2 failed:
SLATS SLOW
FLAPS SLOW
L/G GRVTY EXTN ONLY LDG PERF AFFECTED

● If ENG 1+2 failed:
STEER ENDUR LIMITED

LIMITATIONS ON PFD
ALL PHASES
LAND ANSA
MAX SPEED : 220 KT

DEFERRED PROC
ALL PHASES
> IF JETTISON RQRD :
JETTISON ARM...............................................................................................................................ON JETTISON ACTIVE..........................................................................................................................ON

FOR APPROACH
> JETTISON MANUAL STOP :
JETTISON ACTIVE ........................................................................................................................OFF
JETTISON ARM .............................................................................................................................OFF

> LANDING WITH TWO ENGS OUT :

DISREGARD NORM APPR & LDG C/Ls
LONG APPROACH ..................................................................................................................... PLAN
FLAPS SLOW
Due to the failure of one hydraulic system, only the remaining hydraulic system is available to move
the flaps. As a result, the flaps operate at half-speed.

SLATS SLOW
Due to the failure of the green hydraulic system, only the electric motor is available to move the slats. As a result, the slats operate at half-speed.
BARO REF.....................................................................................................................................SET
MINIMUM .......................................................................................................................................SET
CABIN CREW ..........................................................................................................................ADVISE
AUTO BRK ........................................................................................................................... AS RQRD
SIGNS ............................................................................................................................................. ON

● INITIAL APPROACH :
FLAP LVR ...........................................................................................................................CONF 1
GA PERF MAY NOT BE ACHIEVED WITH L/G DN

● FOR L/G EXTN :
FOR L/G GRVTY EXTN : MAX SPD 220 KT
L/G LEVER..................................................................................................................................UP
L/G GRVTY (EXTN MAX 2 MIN).......................................................................................... DOWN

● WHEN L/G LOCKED DOWN OR AFTER 120S :
L/G LEVER ..................................................................................................................... DOWN

● INTERCEPTING G/S :

FLAP LVR ...........................................................................................................................CONF 2
PACK 1+2 ...............................................................................................OFF OR ON APU BLEED

When engine 1 is failed and ENG 1 FIRE pb is pushed, the left crossbleed valve and the pack flow valve of the engine 1 close. As a consequence, the APU bleed cannot supply the packs.

● FINAL APPROACH :
FLAP LVR ...........................................................................................................................CONF 3
A/THR .......................................................................................................................................OFF
GND SPLRs............................................................................................................................. ARM

FOR GO AROUND : FLAP LVR 1
● AT COMMIT ALTITUDE (500 FT AGL) : SPEED..............................................................................................................REDUCE TO VAPP
The VLS displayed on the PFD takes into account the VMCL-2 whereas VAPP does not take it into consideration. Therefore, the VAPP may be below the VLS, and flight crew may have to decrease the speed below the VLS.
DO NOT ATTEMPT GO AROUND
VAPP is below VMCL-2.


As the procedure is written here, it's quite straightforward, and flows well. But, in the early days of the aircraft, with the original software, it was quite a PITA. Of all the procedures, it probably changed the most over the course of the decade that I flew the aircraft.

 

[Quickstatus]

LAND ANSA

ANSA = at nearest suitable airport?

What are the minimum characteristics of an ANSA airfield?
- suitable runway
- runway length
- suitable weather
- enough time and fuel to reach it
- availability of precision landing
-??

Whereas ASAP = as soon as possible
Does “as soon as possible even if it means landing there might break the aircraft” describe ASAP?

......

 

[jb747]

ANSA = at nearest suitable airport?

What are the minimum characteristics of an ANSA airfield?
- suitable runway
- runway length
- suitable weather
- enough time and fuel to reach it
- availability of precision landing
-??

Whereas ASAP = as soon as possible
Does “as soon as possible even if it means landing there might break the aircraft” describe ASAP?

I didn't keep any of the QF manuals, so I can't give you their exact phrasing. Basically ANSA means an airfield that you could possibly use normally. It doesn't have to be company approved. Weather has to be good enough to get in, but that's about it. Basically, the aircraft wants to be on the ground, but don't go breaking things to get there.

ASAP is both more flexible and dangerous at the same time. It's telling you that the aircraft really, really, wants to be on the ground. But, it's really up to you how you interpret that. If you have a confirmed cargo fire, then ASAP means anywhere, immediately. On the other hand, if you have a fuel/CofG issue (which can be caused by pump issues) then the actual urgency depends upon how much fuel you can access without losing control of the CofG. It's never telling you to ditch, or land in the middle of farm land. That could well be what you end up with, but it's not up to a checklist to decide that.

In the case of two engines out, you certainly don't want to be flying around forever, but there is no need to break the aircraft getting it down. Flying past a shortish but otherwise acceptable runway to get to a longer one would be quite reasonable in most circumstances.

I had an ANSA once, over Pakistan, on the way to London. It was from an underfloor crew rest. Nearest airport was Lahore, and I would have gone there...but we were able to fix the source of the smoke detection, so thankfully nothing was required. Smoke was from a ventilation fan, and turning them off was always one of the first actions.

 

[Quickstatus]

VAPP is below VMCL-2.

Vapp is the Final approach speed when flaps full and landing gear deployed?. does it include a wind correction?

VMCL2 ?? 2 engine minimum speed. The minimum speed at which the tendency to yaw in a 2 engine failure is controllable? because the slower the speed the less effective is the rudder?.

In a 2 engine on one side out scenario:
- s the VMCL2 always? going to be lower than Vapp?
-can you please explain the directive to not attempt a GA when aircraft speed is below VMCL2?

 

[jb747]

Vapp is the Final approach speed when flaps full and landing gear deployed?. does it include a wind correction?

Flap could be full or 3 in normal ops. In two engines out, final flap was 3. I don't recall applying any wind correction in this case. FMC target speeds would automatically adjust, and we could override that with any adjustment that we wanted. I think we could bump it by up to 10 knots (I've forgotten and will ask), but it was very sensitive to change, and only 3-5 was normally needed in gusty conditions. 99% of the time we left it at whatever the FMC wanted.

VMCL2 ?? 2 engine minimum speed. The minimum speed at which the tendency to yaw in a 2 engine failure is controllable? because the slower the speed the less effective is the rudder?.

Vmca2 is the speed at which you cannot control the yaw, with go around power, full rudder, and 5º angle of bank. It was 144 knots in the 380, which is impressively slow given the moment arm and power that the engines had. The 747 was around 159 knots.

Most of the time on the two engine approach, the FMC generated approach speed would be greater than 144 knots, so it wasn't a consideration. But at light weights it could go below. It wasn't much, about 5 knots is all that I remember. When first converting on to the aircraft, we saw this and simply wondered why they wouldn't use 144 as the lower limit, and avoid any Vmca2 issues. The answer we were given was that if you increased the speed by much the aircraft pitch attitude would make a nose gear first landing too likely. I'm not sure of the validity of that answer, but the upshot is that at light weights, your final approach speed could well be below Vmca2. It did wonders for your accuracy.

In a 2 engine on one side out scenario:
- s the VMCL2 always? going to be lower than Vapp?

The FMC will generate the Vapp that it wants, irrespective of Vmca. But, the autothrust is limited by Vmca, and so if the Vapp is less than Vmca, it will not be able to reduce the speed to that figure. That's why we have to manually reset the target speed and fly the power. Vmca2 will be less than Vapp at heavier landing weights, but not at the low end. It's really a mix of behaviours between the FMC and the autothrust.

-can you please explain the directive to not attempt a GA when aircraft speed is below VMCL2?

At a speed less than Vmca2. Apply go around thrust and full rudder, aircraft starts to roll, and you'll need aileron to stop it. But, you may not be able to stop the yaw, and in the worst case, the roll. There is a limit of 15º of heading required by the regulatory authorities for the initial response to a go around (reducing to 5º).

Taking it to an extreme. If you were about 10 knots below Vmca2, and applied full power. Full rudder would not stop the yaw. Neither would full aileron. There would be a pregnant pause, and then the aircraft would probably flick. Lights out. It's a spin entry.

 

[Quickstatus]

aircraft starts to roll

The wings with no engine thrust will have less lift due to the yaw?
Do aileron operation increase drag?

What is the usual 4 engine Vapp?

 

[tgh]

One of the "many" takeaways form this wonderful and continuing discussion.. is the continuing importance of the cough sapiens up the front.
All the computers in the world cannot replace an Hs….. seeking to keep its brethren alive..
Leads to.. listening to the pre flight next time I fly long haul and hoping that the human is up to the job…..

 

[jb747]

The wings with no engine thrust will have less lift due to the yaw?

Only whilst the aircraft is actually yawing. There are a couple of reasons. If you imagine looking down on an aircraft, and you yaw it, the outside wing is actually going slightly faster than the inside one, which serves to generate more lift, and contributes to the roll. The inside is seeing the opposite. Also, on a swept wing aircraft, the yaw effectively reduces the sweep being seen by the relative air flow on the outside, whilst increasing it on the inside. That also contributes to the outside wing making more lift...and so, more roll.

Control surface-wise, on the inside (and downgoing wing) you'd have an aileron input that's attempting to make more lift. That aileron will also generate some extra drag, which reinforces the yaw. So that's adverse yaw with aileron. On the other side, the reverse is happening. The upshot is that your really want to get rid of the yaw, and the way to do that is with rudder. You then correct the roll with aileron.

Not totally relevant to this, is the fact that the down going aileron increases the curve of the wing (the camber). A wing with increased camber makes more lift (which is what we want from the aileron), but also more drag (more adverse yaw). It also has a lower stalling angle of attack. In the rolling aircraft case, the downgoing wing already has a greater AoA than the outside wing. So, if the inside wing is nearing the stalling AoA, then application of aileron to stop or correct the roll could actually have the effect of stalling the wing, which then dramatically increases the rate of roll. This is why pilots are taught never to use aileron to correct wing drop in the stall.

Do aileron operation increase drag?

Yes. And yaw.

What is the usual 4 engine Vapp?

Normal approach speed with 3 or 4 engines is around 136 knots. It varies with weight, but that's it for around 360 tonnes. That's 5 knots greater than Vls (lowest selectable) which is the slowest speed the autothrust is able to go to. Vls is always FMC generated, but Vapp can be overwritten by us, up to a max of 15 knots (I checked that with one of the guys who is still in the game).

 

[jb747]

This is the FMC at about 1,000' during an approach (my last one to London). You can see most of the data we've been discussing.

Correction....it was at 5,500'.