Crosswind Quiz

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Member for

24 years 2 months

Posts: 2,606

An open-ended question to get you thinking and involves postulating a number of factors. Something from last Sunday...

You're testing your favourite taildragging beast out in a full crosswind 180/15 at your 350m strip. Tracking directly towards the 09 threshold your crabbed approach is a seemingly a good 40deg nose off centre line. Your approaches seem alarmingly steep though and a good blast of power to alleviate the sink is required thus somewhat upsetting the final moments of your approach and ultimately landing...

What are you doing wrong and what can you do to improve the situation?

Original post

Member for

20 years 1 month

Posts: 65

It looks to me like a typical wind shear siuation, although the steep approach doesn't seem to fit in with the surface wind direction.

Member for

24 years 2 months

Posts: 16,832

The crab angle is causing your ASI to misread and you are actually far too slow on approach?

Add a few (indicated) knots?

Moggy

Member for

19 years 7 months

Posts: 862

Land on 18, haha. I can only echo Moggy, the crab is causing the ASI to under read.

dme

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24 years 2 months

Posts: 1,324

Provided the crab is co-ordinated, it has no effect on the ASI. It would only be in a slip/skid situation that the ASI is affected, and then it would either under read or over read depending on the position of the pitot with regards to the direction of slip/skid.

This is a really tricky quiz. Provided the approach is flown in a co-ordinated crab down to the fare, at the correct airspeed, I see no reason what-so-ever for the alarmingly steep angle.

What I could imagine on the other hand is an unstable approach. If we are talking Maule with the 235 horse engine, I could imagine the following senario. You arrive on finals high with landing flaps. On seeing that the approach is on the high side you chop the power, and the prop goes to fine pitch creating a huge braking effect. To keep the airspeed you would lower the nose, and the approach becomes very steep indeed. When you arrive close to the ground, you are back on slope and the nose comes up, without the increase in power needed to maintain airspeed, and the airspeed starts to bleed off. What is then needed to salvage the situation is a big blast of power and the resaulting landing will be less than perfect.

Member for

24 years 2 months

Posts: 2,606

It's worth a go isn't it?

You could use less flap to be in less of a flap flattening the angle of approach and encouraging a bit more speed/float, but this all depends on the view over the nose. Sometimes that extra nose down angle is useful :)

Experimentation needed.

Malcolm Payne? Now there's a name I recall. Weren't you an instructor? Something to do with Irv Lee? Or were you the part-time A/G at Wellesbourne? Moggy and (byt jove) myself were trained by Captain Rick at EGBW.

Member for

24 years 2 months

Posts: 2,606

I think you've hit the nail on the head as to why.

Some gen I've picked up and attempted short-landing the Maule. Due to the low stall speed and characteristic of the Maule where the drag curve comes in very suddenly, you can do some very steep approaches and I believe BD Maule's son Ray will teach this technique for an ultra short field landing. Dangerous though because you require quite a lot of power to blast out of that curve into a viable flying airspeed. This is what can unsettle a landing. Far better to do a stable approach every time especially for an amateur like me. Doesn't use that much runway anyway :) Handles like a washing machine landing in a headwind!

Member for

20 years 1 month

Posts: 65

Blue Robin. Yes, I was Irv Lees instructor when he did a flying scholarship in Jersey and I do the occasional day in the tower at Wellesbourne.

Member for

20 years 1 month

Posts: 65

I,ve been thinking about the question a bit more. There is about a thirty degree difference between the surface wind and that at 2000 feet, so with a surface wind of 180/15 it is quite probable that the wind at 2000 feetwould be 210/25-30. This would give you a tail-wind component for an approach on 09 which would , of course give you a relatively high ground-speed and hence a steeper approach than normal. You then enter an area of wind shear and find that your airspeed decreases and rate of descent increases which, in turn, needs a quick power response. I hope this makes sense!