Posts by user "EXWOK" [Posts: 111 Total up-votes: 0 Page: 6 of 6]¶

I'm not sure the 'negative elevator effect' was ever a practical issue in flight (as opposed to on rotation) - the response was entirely normal and I reckon that the increase in lift is near enough instantaneous. Aircraft with tailplanes would have a similar theoretical effect.

I don't recall hard landings being an issue on windy days - quite the opposite.

If there was an influence due to wind I would say it's more likely to be that in the gusts one may be tempted to 'tweak' the attitude: Putting the nose down by half a degree at 50' would have very disappointing consequences....

From memory, we had 4 speeds available:

Vref 'Normal' final approach speed (actually not used that much)
Vref+5 Engine out speed
Vref+7 Noise reducing approach speed (used as often as possible)
Vref+10 If the headwind component was over 25(?)kts

Most were at +7.

Vref was least nice - you had a higher attitude to start with, and needed more flare, which meant tail clearance was tight. It also meant that if you picked up a high RoD at 50' or so, it was VERY difficult to catch. One *could* add a bit of thrust at 30' or not close the throttles at 15', but this was not without drawbacks.

Vref+5 was better - the reason it was used was to give better g/a performance on 3 engines (there are obviously a lot of square laws at play here, because it made a significant difference).

Vref+7 was used off pretty much every ILS approach to a decent length of runway, where we would carry out a noise-reducing approach. This is probably explained elsewhere in the thread. These days it would be called an unstable approach! It gave you more lift margin into the flare and also more room to make pitch inputs (i.e. space for another half- to one- degree of flare).

Vref+10 was for windy days. I liked it! If you arrived at 40' in the right place, you basically just held the attitude and the ground effect did the rest. It did still *feel* like you had flared, as the ground effect would push the nose down and so back stick was still required to hold the attitude.

I hope that has answered CliveL and Megan's questions somewhat?

It would appear so....but I wonder if Vref+10 came about as a result of earlier experience and that was the source of the story?

I get what you mean about the height response at the cockpit vs flightpath response....but given that we're talking about landing, then it's the height of the undercarriage that matters.

FWIW, like all long-bodied aircraft, a last-minute pull has the capacity to drive the u/c into the ground harder because the pitch change happens before the flightpath change. That could well be exaggerated by 'negative elevator' effect.

A video of a landing could be quite telling if you could see the elevons - there's a very marked and increasing 'up' input to counter the pitch down from ground effect. I suspect that, in ground effect, this negative elevator effect would be swamped by all the other things that are happening.

A slightly tongue-in-cheek comment, Megan.

The BA Ops Manual requires an approach to be fully stable at 1000'R. It used to be slightly more relaxed, but even then a 'reduced noise' approach was an exception to the policy.

Basically we flew at a higher speed (190kts) until 800', then reduced speed to achieve final approach speed at 300'.

This had two benefits - thrust required at 190kts was a lot less than 160kts so flew a quieter and less-thirsty approach, and the portion between 800' and 300' was quieter still.

Vref+7 gave better control and performance margins at the end of this manoeuvre - I'll try to find a reference as to why +7 came about (I recall there was a specific reason for that number, but not the detail).

AB had them removed for balance reasons, given that it has no interior.

It must make a fair difference: On average, much of the 'interior' is ahead of the CG and remember AB has no cockpit, which is a fair chunk of weight a long way forward,

I vaguely recall that AB was filled up with old 'High Life' magazines initially.

Tanks 5 and 7 inlet valves have an \x91override\x92 position, do they not?

During the t/o roll, while the trim transfer pumps in 11 will be off, the de-air pump would allow flow through the trim transfer pipes to any tank with an open valve. The valves *should* be closed, unless someone had been creative with any override selections and failed to return them to normal.

I\x92m not sure we *know* the tank 11 txfr pumps were on.

The 5/7 inlet valves were in the override position.

Even if the T11 txfr pumps were off, the de-air pump would pump fuel to the trim txfr pipes and hence to 5/7.

All assuming I remember the report correctly.

The nub being, if you \x91hide\x92 fuel and forget to return the 5/7 inlet valves to normal, you will still feed 5/7 even if the 11 pumps are off.

Favourite: OAF for fuel burn and subjective personal preference.

OAC second for the reg!.

OAD was indeed the schedulers' favourite for long charters although I have to say that I didn't have fewer or greater tech issues with it c.w. the others. Def. not a favourite on BGI because it burnt a bit more fuel than some others (e.g. Fox and Golf).

PATTERN-IS-FULL...

A pretty accurate summary, I'd say; nice work!

One correction I'd make:

Is over-egging the pudding somewhat. There was a significant penalty on 3 engines, but it was hardly a 'fuel emergency'. In my experience it was more of a fuel irritation.

My current work aircraft also suffers a significant range penalty with an engine out, but that hardly matters because we will be landing at the nearest suitable airport. Concorde had an even bigger range penalty with two engines out (although we always had fuel to reach an airfield in this situation) but, again, with two engines out it still had far more range flexibility than the 777...

BIG BORE FOUR -

Remember we were never at MTOW for long in this machine! Initial subsonic cruise ex-LHR was 280-300. In the case of engine failure enroute, it usually ended up in the mid-30's (with its subsonic 4 engined contemporaries).

The process explained in the extract from the OM is worth thinking about...you fly Mach, but the IAS still plays a dominant role on drag as you climb. Most unlike conventional types.

IIRC, it was...but I can't remember it being done while I was on the fleet.