Landings in gusty conditions

[Major Major]

Hmm, it be getting gusty out there over the next few days...

Let's say I happen to be flying a PA28-161 out of Barton on 27L and the wind was 270/15G30, so it's right down the runway but it's gusty.
Now, normally I'd drop the final stage of flaps on finals over the motorway at about 600ft (give or take) and would approach at 65Kts.

However, when it gets gusty I'm not entirely sure how to handle it. On the one hand, I've been told to nail that approach speed no matter what, so surely I'd be adjusting attitude constantly depending on what the wind was doing.

On the other hand, a voice inside my head is telling me that if I'm nailing 65Kts and the wind drops by 15Kts, I'll suddenly have 15Kts less IAS and the stall warner will probably come on...so the temptation is to go in faster, say at 70Kts, for a bit of a safety margin.

What do you guys do?

[S-Works]

Your first answer was correct almost, adjust with power, choose the position on the runway you want to land on and keep it in that position on the windscreen with power and small attitude adjustments. If you put the extra knots on for the "wife and kids" the wind drops close to the ground, on a short runway where do you intend on getting rid of the excess speed? The hedge most likely.....

[Major Major]

Thanks Bose...Given that hedges are oft mentioned as good at retarding aircraft, I've often wondered why they don't fit arrestor hedges to aircraft carriers...it would make for some nice greenery...

[big.al]

arrestor hedges to aircraft carriers

Well that's an excellent idea - they work great at Netherthorpe, so why not?

[Speedbird48]

Hi Major Major,

Where were you when the instructor was teaching this stuff, or better still where was the instructor, if indeed he taught it??

A rule of thumb is to add 1/2 the gust factor to your normal speed.

Are you sure that you want to use "the final stage of flap" under those conditions??

Watch for inbound!!

Speedbird48

[S-Works]

Half the gust factor only works for lighter winds and long runways. Example, my Cessna approach speed is 70kts. Today wind is 18kts G30, half of gust factor is 6kts giving an approach speed of 76kts. Enter ground effect wind is in the ebb after a gust and you are way to fast.

It is much better to fly the correct numbers in the correct manner.

But hey what would I know.

[Johnm]

I was taught the half gust factor trick so in the example quoted difference between "steady" speed and "gust speed" is 15 knots so add 7.5 knots. However that's approach speed and you'd be wise to come over the threshold at less than approach speed if you don't want to float forever in a Warrior. The little bit of extra momentum on the glide slope helps avoid too much corrective throttle and attitude for us less than skygod pilots whenit's gusty.

My similar Archer would in the conditions you describe fly base at 75 kts final at 70 (instead of 65) and still cross the threshold at 60 but I'd be ready for a (very) little blip of throttle to cushion the touch down if the wind drops at the last second.

In fact once set up on the final approach (visual) I don't really look at the clocks and dials I look at the picture in front of me and try keep it constant until I'm ready to close the throttle completely and land.

[gcolyer]

I sort of agree with Bose.

The PA28 dakota I use has an approach speed of 77 kts. I always add the 1/2 gust factor and usually have no issues.

However the other day sure as hell as Bose describes the ebb I ended up to fast when trying to stop on a short and narrow runway, which resulted in some hefty breaking and lots of rudder pedal work.

Bose I beleive you know the aircraft and the group as the other 3 memebers are on the PPL/IR committe.

[Major Major]

I should clarify that I'm still a student and my understanding of my instructor's guidance thus far has been to nail the numbers all the way down (both on the grass and on the dials), as per Bose's advice.

I don't want to start a 'bash the instructor' thread as the half gust factor rule of thumb may well have been taught and I've just been too thick to get it - but bearing in mind the last time it was gusty we were on the (even) shorter 20/02, it might have been thought to be inappropriate given the extra few knots that would be carried down to the threshold.

You're right on the flaps; in the conditions we're discussing I'd probably not drop that final stage.

GColyer has more or less described how I end up in these circumstances - lots of rudder work and heavy braking, which is fine until you want to get down on 20/02 after a recent downpour...

It sounds like I need to be able to do both depending on circumstances - and if I can get my thottle/attidude control good enough to fly the correct approach speed, then I can certainly add a few knots for the wife and kids if I've got a 1000m runway to play with.

[Will Hung]

My advice, for what it's worth, is, forget drag flap, two stages is all you want in gusty conditions in case you have to go around. Set yourself up nicely on base at 70, don't try adjusting for IAS too much as it might be up and down like a whores drawers, then just do what you've been taught to get to this stage, control your height with power. Simple. (although it wasn't as a PUT) ! Happy landings.

[S-Works]

Adjusting speeds outside the POH is just poor pilot skills and you will get caught with your pants down eventually.

Nowhere in my POH does it say anything about adjusting the speeds for gusty conditions. It does state that all figures in the POH are subject to the aircraft being flown exactly at the stated numbers.

Learning to fly at the correct numbers is all about becoming a good and safe pilot, adding rules of thumb and old wives tales is about being an average pilot. Most of the time the average pilot gets away with it, the times that they don't makes for entertaining reading in the AIB reports or to often sobering reading...........

[flyme273]

Airliners rule is to add 1/2 the headwind plus all the gust (above the headwind) up to max 20kts.

so in your example (app70 kts Hwind 18 kt G30) add 1/2 of 18 kts plus 20 kts for gust = 29 kts. Approach speed is therefore 98 kts.

I know this will meet with some controversey and it does seem too fast.

However lets analyse what we are doing. First the gust- it means exactly that. One minute its there, the next its gone - very dangerous. If one only adds 1/2 gust then next minute one will have minus 1/2 gust - not safe.

The headwind correction partly restores the ground speed so no risk of running out of runway.

This is for Approach say 4 mls Dme to near threshold. Nearing threshold start to reduce power and round.

In practise for a Piper, I would certainly add the gust correction and maybe ease up on the headwind and use 1 or 2 stage flap subject to runway.

I would question the wisdom of flying a light aircraft on a day with G30 knots at the airport - that is a lot of wind, particularly as you are a student. I don't think I would get airborne.

flyme

[Wrong Stuff]

It's been a while since I've looked at a Cessna handbook, but from what I remember that surprises me, Bose-X. In their Operating Details section (section 2 in the old days) Cessna used to give a recommended approach speed range and suggested you adjust the approach speed dependant on wind speed and turbulence - ie gusts. Perhaps yours is a later version and they changed their recommendations.

[Major Major]

FlyMe;
Some good points there but I worry about carrying too much speed into a potentially slippy <600m grass runway, even with the ground speed due to the headwind.

Equally, if I'm going to fly the POH numbers precisely I worry about reacting to quick gusts in sufficient time to maintain the POH airspeed.

If it's straight down the runway I've been up in G30 before. I agree that a substantial crosswind would make it unflyable and I'm well aware of my own crosswind limits as well as the aircraft's.

[Contacttower]

At 65 knots in a PA28-161 you will have some difficulty keeping on the centre line in a gusty crosswind...simply because at that speed with full flap it gets quite vunerable to turbulence and tends to 'wallow' a bit in the air. I would come in with just two stages flap at 70, and slow to 65 as you come over the hedge. No faster though....the tapered wing PA28s when light will float for ages in ground effect.

[Saab Dastard]

Airliners rule is to add 1/2 the headwind plus all the gust (above the headwind) up to max 20kts.

I don't think that it is really appropriate to compare SOPs from airliners to light pistons.

Almost all airliners these days have jet engines, and as you know, jet engines have a considerable spool-up time, so it is not really practical to adopt the same "adjust RoD with power" that bose-x and others have described as the correct op for piston singles.

Airliners also have considerably more inertia, which is also a big difference to a light piston, in that it takes more power for longer to change the trajectory.

I would think that the majority of runways (of course there are many exceptions) for airliners are long enough to accomodate a longer landing run with additional / excess speed.

Finally, not many light pistons have airbrakes and / or spoilers to dump lift!

SD

[Gertrude the Wombat]

Easy.

I fly for fun.

G30 isn't fun.

If it says G30 I don't go flying.

(Actually I did the other day, when it was G30 mostly across the runway. But this was an IMC lesson so I told the instructor he could do the landing. He proceeded to show off by running quite a long way on one wheel, not something I've ever been taught to do.)

[Contacttower]

He proceeded to show off by running quite a long way on one wheel, not something I've ever been taught to do.)

Certainly I've been taught to touch down on the into wind wheel first in a strong cross wind....but as for running a long way on one wheel, that is showing off .

[IO540]

It's a fact of life that when it's windy it is more difficult to fly a stabilised approach and it's difficult to do the last bit too. One just has to be quite proactive with the controls - often this looks alarming to passengers who are used to you holding the yoke with two fingers. Crucially one must maintain the "glideslope" while very regularly checking the airspeed, and if it starts to change away from the target then the engine power must be quickly adjusted - all the while one is using the controls to keep the plane on the line of the approach (laterally and vertically).

Usually, the last few feet are OK because there is much less wind ON the runway than say 20 yards up.

It also helps (in terms of pilot workload) to be correctly trimmed for the landing configuration airspeed when still high up (shortly after base to final turn i.e. about 1000ft AGL) because it tends to not be too bumpy up there. Then, when it gets rougher as one descends further, there isn't any need to fiddle with the trim, and in any case it would be a waste of time because one can't trim when the thing is going all over the place.

And the more wind there is, even if straight down the runway, the more wind shear there will be. So one has to watch the airspeed extra carefully. I personally don't "add extra" for this but then I fly a 250HP plane which has loads of power. In a Warrior, I would be wary of landing with say a 40kt wind because at 1000ft it is likely to be 70kt which is 30kt of total wind shear; in fact more because the wind is measured at the top of a 10m pole and there will be considerable additional wind shear in those last 10m of height. In such a case is is going to see 40kt of airspeed gradually disappear between starting the final and touching down. In such a case one should probably add 10-20kt to the approach speed.

I've done about 700 landings to date (7 years, 850hrs TT). Only one go-around so far due to bad technique. So whatever I do seems to work for me.

[FREDAcheck]

Bose wrote:

Nowhere in my POH does it say anything about adjusting the speeds for gusty conditions. It does state that all figures in the POH are subject to the aircraft being flown exactly at the stated numbers.

Good idea to stick to what the POH says, I'm sure. The Cherokee owners handbook says:

"In high wind conditions, particularly strong crosswinds, it may be desirable to approach the ground at higher than normals speeds with partial or no flaps"

However all the landing performance charts are based on approach at 1.3VS0. Hence, approaching at higher than 1.3VS0 will result in longer landing roll.