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-   -   Buff crosswind crab taxi (https://www.pprune.org/military-aviation/654565-buff-crosswind-crab-taxi.html)

West Coast 4th Sep 2023 01:53


Originally Posted by 757Bob (Post 11496553)
I’m an old BUFF driver from the ‘70’s. In that time frame we were restricted to airfield with 300 ft. width runways. The crosswind crab system was never contemplated as an aid to turning sharp corners, or taxiway maneuvering, but permitted us to land in 45kt direct crosswinds. The crab setting is precomputed and applied when aligned for takeoff, and removed when slowed to taxi speed after rollout. I had a copilot apply the setting in the wrong direction once. He saw his error, and cranked it all the way the other way while we were rolling. A thrilling low speed rudder dance ensued, similar to the video.

Were there any issues with compressor stalls on the downwind wing/engines?

wiggy 4th Sep 2023 06:42


Originally Posted by Jhieminga (Post 11496165)
So what bit of the airframe needs to be on the centreline? Not the flightdeck I guess.... that might be the challenge in landing like this.

Apologies if I'm teaching you to suck eggs but to some degree (SWIDT) it's much the same, at least until the actual de-crab, when flying anything long bodied on an approach with the drift on. You fly down the approach with the flightdeck tracking offset to the upwind side of the centreline.

On those if you've got it right then as you flare and push the drift off the aircraft yaws and the flightdeck returns to the centreline..I'm guessing for the Buff guys they flare and accept the offset remains on touchdown

ORAC 4th Sep 2023 07:06

Crosswind take-off…..


Jhieminga 4th Sep 2023 08:18


Originally Posted by wiggy (Post 11496773)
Apologies if I'm teaching you to suck eggs but to some degree (SWIDT) it's much the same, at least until the actual de-crab, when flying anything long bodied on an approach with the drift on. You fly down the approach with the flightdeck tracking offset to the upwind side of the centreline.

On those if you've got it right then as you flare and push the drift off the aircraft yaws and the flightdeck returns to the centreline..I'm guessing for the Buff guys they flare and accept the offset remains on touchdown

No need to apologise and thanks for the clarification. I'm strictly a small airframe driver and I had forgotten about the similarity to a long-bodied airliner while crabbing. Makes sense now.

As for rotation on a BUFF, the arm between CG and rear wheel set is very much larger than on a regularly geared airliner/military type, requiring a significant downforce from the tail. One more reason for the built-in angle of incidence on the wing as you would never be able to achieve the same rotation with this size tail as on a civil airliner.

ORAC 4th Sep 2023 08:34

Nice video of how the a B-52 wing incidence works during landing.



Vzlet 4th Sep 2023 11:00

This helps explains the B-52's remarkable range -- it flies downhill the entire way!


Originally Posted by ORAC (Post 11496407)


pithblot 4th Sep 2023 12:47


Originally Posted by DaveReidUK (Post 11496415)

Is that gauge anything like the Fortunate Son switch?

757Bob 4th Sep 2023 17:03

BUFF takeoff and landing
 

Originally Posted by West Coast (Post 11496713)
Were there any issues with compressor stalls on the downwind wing/engines?

The crab angle, even in a strong crosswind, isn’t enough to induce compressor stalls. The J-57/TF-33 (depending on aircraft model) engines were straight turbojet or low bypass turbofan. Very rugged.
With regard to takeoff and landing characteristics, because of the wing incidence angle, the airplane would try to fly off tail end first if you didn’t apply back pressure at VR.
As you approached the flare for landing, if you were trimmed for approach speed, you’d run out of up elevator authority trying to flare. Trimming in the flare is required to keep from hitting front trucks first. ‘Getting a nose gear’ results in a dramatic bounce. Trying to salvage it often produces a serious PIO. Go around definitely recommended.

dixi188 5th Sep 2023 16:26

I flew with a guy off C5 Galaxies. He said the early ones had a crabbing landing gear for cross winds, but after an event when one landed with the wrong way selected, the system was disabled, as the de-crab was no big issue.

DaveReidUK 5th Sep 2023 16:48


Originally Posted by dixi188 (Post 11497666)
I flew with a guy off C5 Galaxies. He said the early ones had a crabbing landing gear for cross winds, but after an event when one landed with the wrong way selected, the system was disabled, as the de-crab was no big issue.

I think the rearmost MLG leg is still able to castor.

Jhieminga 6th Sep 2023 08:06

At C-5 masses you don't need a cross wind gear, it just beats the runway into submission.

stilton 6th Sep 2023 08:13


Originally Posted by DaveReidUK (Post 11496415)

Ok, I’ll bite

You posted the picture, care to explain ?

DaveReidUK 6th Sep 2023 09:31

Simply illustrating how vocabulary changes over time. :O

stilton 7th Sep 2023 05:21


Originally Posted by DaveReidUK (Post 11498053)
Simply illustrating how vocabulary changes over time. :O


You are ducking the question, do you know what this instrument is for then ?!

DaveReidUK 7th Sep 2023 08:37


Originally Posted by stilton (Post 11498469)
You are ducking the question, do you know what this instrument is for then ?!

Rad alt.

Jhieminga 7th Sep 2023 13:58

Have a look at 1:18 in the video on this page https://www.gettyimages.nl/detail/vi...tage/816064990
It shows an Autoland sequence on a HS Trident, including the Rad Alt indicator shown above.

ORAC 7th Sep 2023 17:40

I believe the picture was posted in response to Stillton in #10 and in particular the use of the term “kick-off Drift”, rather than reference to the function of the instrument itself in the Trident blind landing system.

Terminology and the use of words changes over the years.

DaveReidUK 7th Sep 2023 17:46


Originally Posted by ORAC (Post 11498864)
I believe the picture was posted in response to Stillton in #10 and in particular the use of the term “kick-off Drift”, rather than reference to the function of the instrument itself in the Trident blind landing system.

Terminology and the use of words changes over the years.

Yes, sorry I couldn't resist. :O

stilton 8th Sep 2023 05:17


Originally Posted by DaveReidUK (Post 11498867)
Yes, sorry I couldn't resist. :O

Lovely old film


Terminology has changed, a pilot shouldn’t be told to ‘kick off drift’ any more than he or she should be told to flare by yanking on the yoke

ShyTorque 8th Sep 2023 05:33

Surely on a B-52 there is always a yank on the yoke….


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