Different T.O & LNDG xwind components for H.S. Trident

[vincenzino montella]

Hi everybody,
I have this question following a story by a Trident pilot during the 80s...he declared that the Trident had different cross wind components for take off and landing due to the offset position of the nosewheel gear.
As I can't figure out this behavior and after I made a lot of researches on the net, this will be my last attempt on this issue: anybody has any information?
Thank you very much for attention.
Happy New Year to everybody!

[Meikleour]

I think what you are referring to was the Trident 3B which did have a different crosswind limit on each side due to the placing of the boost engine and the APU. I believe the other marks ie. 1 & 2 did not have this "quirk". I am sure more knowledgeable posters will confirm this.

[vincenzino montella]

Thank you very much for your comment, Meikleour!
Actually I was caught by this "quirk" from that great plane, never heard something similar in my long career...about 40 years...
Can you remember any detail on that particular "geometry" affecting the different response on crosswind components?
Thank you again.
Have a great New Year.

[Flap40]

Does the OP mean a different x-wind from the left or right or the same from left and right but different for T/O and landing?

I have it in my mind that the 146 had a different for T/O than landing but I can't find my manuals. I last flew it in 1998 but I seem to recall 31kts for T/O and 35kts for landing.

[vincenzino montella]

Hi, Flap40,
What I recall of the story it's just a difference between left and right crosswind components on that particular model for T.O. & LNDG.
Thank you for your interest.
Happy New Year to you!

[oftenflylo]

I think you'll find the crosswind limitations on Trident 3 were only for take-off. We used to take them to 'wrong' end at Heathrow, wait for a batch- stop the 28L deps & launch the batch of T3 from 10R.
dH used to take a plane back to Hatfield in winter & never actually resolved the problem. One thought was the nosewheel door on the longer fuselage was creating the problem.

[Discorde]

Trident 3 x-wind limits (http://steemrok.com/t3%20xwind)

[Flap40]

Interesting. What was/is the skimming technique?

[DaveReidUK]

One thought was the nosewheel door on the longer fuselage was creating the problem.That's an interesting idea. The NW door that stayed open on the Trident when the gear was down was the port one, so that could account for a lower limit when the x-wind was from the left.

The suggestion that it was related to the boost engine and/or APU position on the T3 is a bit more difficult to understand, given that both were on the centreline, but maybe there's more to that than meets the eye.

[Offchocks]

The NW door that stayed open on the Trident when the gear was down was the port one, so that could account for a lower limit when the x-wind was from the left.
I don't understand how that could be the reason, does anyone have an explanation?

I was also wondering what the skimming technique was.

[DaveReidUK]

I don't understand how that could be the reason, does anyone have an explanation?

Well sadly we're unlikely ever to be able to put it to the test, but I'd suggest that a 30kt x-wind from port, impinging directly on the Trident's NW barn door would produce rather more of a yawing moment than the same wind from starboard which would hit the NLG leg first. Particularly given that said door hangs at about 30° from the vertical.

Whether that's enough to account for the asymmetry in the x-wind limits, I'll leave for you to judge.

Alternative explanations welcomed, needless to say.

[con-pilot]

Interesting. What was/is the skimming technique?

Yes, I've never heard of that.

[oftenflylo]

I am SO impressed that Discorde has kept his manuals - just in case they restore a T3.
There was a slightly different nose-wheel door arrangement on various marks of HS21. After the loss of Turkair Dc10, other aircraft often reported that the Trident doors were not closed. This occurred when say a T1 & T3 were at the hold - we used to have to send a vehicle out to inspect.

[Discorde]

On the T1 the right door remained open after nose gear extension. On the T2 and T3 it closed again. Google images of DH121. HNY!

[Meikleour]

DavidReidUK: The fact that the limits are only different for the take-off case suggests that it is the effect of the operating boost engine that is at play here. (boost always off for landing ) Perhaps the air intake for the boost engine affected the airflow around the fin and rudder?

[Discorde]

Hi Meikleour

The boost had intake doors on both sides of the fin, mechanically interconnected, suggesting symmetrical airflow patterns. The APU air inlet was on the left side of the fin and its exhaust gases exited vertically above the centre engine intake. But the T/O limits applied regardless of APU and or boost operation.

I can't remember what the 'skimming technique' was or actually using it and thus far have been unable to find any reference to it in the manuals. [/NERD]

[DaveReidUK]

Perhaps the air intake for the boost engine affected the airflow around the fin and rudder?The RB162 had an intake on both sides, and I'm sure those did affect the airflow, but it's not immediately obvious why the effect would be asymmetric necessitating different port/starboard x-wind limits.

Edit: Discorde beat me to it. :O

[Discorde]

Skimming technique: a very faint bell rings: it might be the technique of prematurely lifting the nose wheel off the runway prior to rotation proper - on contaminated runways to avoid spray ingestion into the engines? Obviously this procedure would reduce yaw control through loss of nosewheel traction.

[DaveReidUK]

On the T1 the right door remained open after nose gear extension. On the T2 and T3 it closed again.

If I recall correctly, on the T1C the refuelling panel was in the NLG bay, hence the need for access on the ground, whereas on the T2/T3 (and the T1E, I think) it was moved to one of the MLG bays.

Great thread, by the way, brings back happy memories.

[oftenflylo]

And when there were 20+ Tridents taxying at night - the only one to be recognisable was the T1E, because it had two anti-coll lights on the top of the tail. otherwise we were all guessing!

[Meikleour]

Handling the Big Jets ( 3rd edition ) by DP Davies shows on plates 20 & 21 the skimming takeoff technique used for slush for a Trident.

[vincenzino montella]

Hi Discorde,
thank you very much (and my compliments) for having stored such important information (for us, "white-haired pilots" and "history and nostalgia" addicted).
I appreciate the fact that those limits apply for T.O. only and now comes the question: why not for landing too? Maybe, my guess brings to me a (stupid) conclusion: with that "geometry", would the xwind component (from the port side) affect less the landing roll due to a reducing speed in the landing roll, in a way that the lateral control could not be a problem? For sure my assumption can be wrong, but I put on the table as a topic for further discussions.
I saw in your following entry that you talk about the "skimmink technique".
After some reasearches on the net, I found an accident report (flight BA incident 1E, G-AVYD, happened at Bilbao airport (Spain) on 15 september 1975).
In short (the report is avalable on the net), the accident happened during a take off on a RWY covered with "puddles" and a momentary deceleration due to the drag of water puddles around V1 was misunderstood as an angine failure.
Following the "äbandon" take off order, the aircraft experienced some acquaplaning and the captain (who later stated: "marked deceleration compatible with a loss of engine power"),considering impossible to stop before the end of the RWY, decided to veer off to the port side. The happy result was that no one was injured.
Information reported on the company manual, regarding "T.O. from contaminated RWYs - PADDLES", required the use of "full thrust"and the "use of skimming technique"...maybe the meaning is "to skim the milk"...eehmm...sorry..."the water", to stay out of it?
Again, searching the net, some pilots report that the technique calls for a "weight off" of the nosewheel for T.O. and they say that it was introduced by RAF for early jet fighters.
A Vampire pilot reported, from his "Pilot's notes": äs soon as the aircraft reaches a speed of 60-70 knots IAS, lift the nosewheel just clear of the ground, then at 82-87 knots ease the aircraft off the ground".
The early De Havilland Comet airliners used the same technique: to lift the nosewheel just clear of the runway as soon as the elevators became effective.
It happened, unfortunately, that some pilots over-rotated early in the run in order to get the "nosewheel skimming" the runway and the aircraft failed to accelerate: there were two major accidents using this technique.

I don't know if I put more confusion on this issue, anyway it will be nice to talk further on this matter.

Happy New Year again.

[vincenzino montella]

Thank you, Meikleour, I have that magnificent book somewhere buried at home...I'll start a search after these days of "drinking sessions"...:)
Happy New Year

[DaveReidUK]

Information reported on the company manual, regarding "T.O. from contaminated RWYs - PUDDLES", required the use of "full thrust"and the "use of skimming technique"

Just to clarify, Northeast's ops manual mandated use of the skimming technique, in conjunction with the optional 11,400lb Spey 511 rating, where puddles on the takeoff run exceeded 12mm deep or 6m long.

The investigation report criticises the Bilbao commander's failure to use the above measures, given that he was unaware of the depth and extent of standing water, although it draws no conclusion as to whether their use would have prevented the accident.

https://assets.digital.cabinet-office.gov.uk/media/5422fe7ce5274a13170009c1/8-1977_G-AVYD_.pdf

[scotbill]

Thje skimming technique was intended for contaminated runways to avoid engine ingestion.

Basically the nose wheel could be lifted off the tarmac after 80 knots but care was needed to ensure the nose was not allowed to get too high. The technique could be practised on dry runways and possibly had the bonus effect of giving the first class passengers a slightly more comfortable ride on the runway.

However, God had already provided the HS121 with an offset nosewheel so that it didn't have to ride over the centre line lights -- although some pilots failed to take advantage of this.

[DaveReidUK]

The skimming technique was intended for contaminated runways to avoid engine ingestion.Though the ops manual did mandate a visual compressor check before the next flight, just in case it hadn't. :O

The other intent of the skimming technique was of course to reduce drag and thereby improve acceleration during the latter part of the takeoff run (a factor in the Bilbao accident).

[vincenzino montella]

Thank you to all of you, guys!
Happy New Year

[Discorde]

However, God had already provided the HS121 with an offset nosewheel so that it didn't have to ride over the centre line lights -- although some pilots failed to take advantage of this.

On an aircraft with conventional nosewheel geometry the handling pilot usually keeps the centreline lights running directly below him or her. If the captain is driving the n/w will run a little right of the lights and vv for the first officer.

[DaveReidUK]

However, God had already provided the HS121 with an offset nosewheel so that it didn't have to ride over the centre line lightsI've often heard the urban myth about the offset NW to avoid the runway lights, but I hadn't realised it was a result of divine intervention. :O

[Offchocks]

Thanks Meikleour and scotbill, now all we have to do is find out the reason for the differing cross wind limits!

[oftenflylo]

Well, as the Hatfield guys couldn't find it back in the seventies - it'll be great if the folk on here find it!