Landings in gusty conditions

[FREDAcheck]

So the only answer is to nail the 70Kts approach speed all the way, don't drop the last stage of flap...

If you don't drop the last stage of flap, then 1.3Vs is bigger than with full flap. For example, with a Cherokee, Vs reduces by about 3kt with each extra stage of flap. Hence the "book" numbers are greater with reduced flap. However, as Bose warns, beware of short runways. Most POHs will give charts of runway length required at various landing weight, temperature and head/tail wind and with a specified flap setting. If you decide to add half the gust headwind component (or half the total gust component) then you have more stall margin if the headwind drops in a gust, but as Bose points out, you're then outside the manufacturer's conditions for landing length. And ground roll increases with something approaching the square of the ground speed at touch-down.

Bose and other experienced pilots probably don't need the extra margin as their reactions will be quick and accurate in gusts. Less experienced pilots might prefer the margin. I don't see anything wrong with that - provided the runway length is sufficient, as Bose points out.

[yoohoo748]

A plane is a plane. Lift, thrust, drag and lift. Lose your headwind component and you may be in for a world of hurt. An additive will ensure safe operations.
I can't recall what the manuals said in the light singles or twins that I have flown, but I do recall adding 'some' when it was windy and gusty. On the MD-83 we added either ½ of the head wind component or all the gust, which ever was greater, to a max of 20 knots. On the B767 we do the same, but combine the two.(again, max 20kts) Keep in mind, for those of you that are worried about over running the stopway, that with the additives your ground speed will be reduced by your headwind component. Thus, if your approach speed is 70kts, and you add 15 because the wind is 20 gusting 25, then your approach speed will be 85, but your ground speed will be 65. Once crossing the threshold, your additive for steady state wind is to be bled off and your correction for gusts maintained, so that your IAS will now be 75, and ground speed will be 55!!!
Any average pilot should be able to, without much effort, stop his a/c in a shorter distance on a nice gusty and breezy day in shorter distance than on a calm day. Perhaps on a light a/c your additive might be 5 or 10kts max, or something like that... I don't know. Play it safe. Don't try to be a hero. If the approach looks like it is going into the toilet, abandon the approach and try again.
Oh, and I hope my math was correct for the above now that I am looking back up at it. Please correct me if I am wrong.
Slopey... B767 company limit 33kts dry. MD 83 was 30 demonstrated. I think.. at least that. Did that with no problems. HS748 was 30, again if memory serves correct. Did that too, no problem... very nice handling plane. Worst wind I saw was in Churchill, about 30 or 40 degrees off the runway 49G60. Made for a very short landing. I'm not bragging here as I do believe that I am not an elite pilot of any sorts. Just been there and had to do that.
I hope this helps. Cheers.

[S-Works]

Except that wind speed is given 10m above the runway, the speed 10m down can be significantly lower. In a 737 etc that makes little difference in a spamcan it is a huge difference.

You only have to look at the AIB reports to see the number of people who have made this mistake on short fields.

There is no way I would want to be whistling along the runway at barton in a cherokee at an IAS of 75kts regardless of the headwind component at 10m......

As has been pointed out several times in this thread, the additions work fine for large aircraft on large runways, on a small aircraft the type of increases you are talking about are massive increases over POH values.

Perhaps the reason why airline pilots often struggle with a return to light aviation after a period away.............

[DFC]

Aircraft X has a stall speed of 50Kt and an approach speed of 65Kt with landing flap. With a level grass runway, including the safety factors, the landing distance required is 600m

Flight Manual recomended technique is a steady approach at 3deg glideslope to cross the threshold at 50ft and 65Kt. At this point the throttle is closed.

Now let's say that the wind is 10G20.

Approach speed 70Kt (Vth + gust/2)

Ground speed at the threshold is;

60Kt with no gust and 50Kt with the full gust.

Now if the aircraft can land in 600m when the groundspeed at the threshold of 65Kt can someone please tell me why it will run off the end when the groundspeed is less.

The only reason why adding half the mean wind is not recomended is the problem with trying to get rid of all that airspeed.

As a pilot you are expected to cross the threshold at a speed of Vth +15/-0Kt. If you can't do that the CAA will not give you a licence.

15 knots fast in 0 wind will eat into your 1.43 safety factor. However, using the half gust factor maximum 10Kt, you would never be that fast if you fly accurately.

The big jet on the big runway can be even more limited in terms of performance. In other words, it needs every metre of that big runway.

Regards,

DFC

[S-Works]

because when the CAA give you a license those tolerances are fine within your experience. As your experience increases those tolerances decrease.

because as I pointed out the wind is given 10m above the threshold, if you are carrying that extra speed at the tarmac or grass on a short runway you may have a problem.

There is nothing difficult about flying the correct speeds and developing the skills to fly the correct speeds in all conditions.

[DFC]

because as I pointed out the wind is given 10m above the threshold, if you are carrying that extra speed at the tarmac or grass on a short runway you may have a problem.

There was I thinking that the approach ended at the 50ft point crossing the threshold and from that point on was the landing.

If you read most cessna and piper manuals, you will find thew following;

Steady approach to cross the threshold at 50ft, Throttle closed landing.

If you maintain your approach speed to the tarmac then you are not flying as the manufacturer intended.

What we are talking about is a safety adjustment to the airspeed to ensure an adequate margin above the stall during thre approach to the 50ft point.

I don't know about your aircraft but when I close the throttle, drag takes over and the aircraft slows (quite quickly with landing flap).

Before arguing about exact book approach speeds, one has to remember that in many cases, landing distances are only published for landing flap settings. Using zero flap with no performance figures is just as far outside the flight manual performance figures as adding 5 or 10 kt to the approach speed with landing flap.

The wind is measured at 30ft because it is clear of errors caused by surface effects in the vicinity of the annenometer and since the landing starts at 50ft, is a good indicator.

Regards,

DFC

[S-Works]

Silly me, of course you always know best. I will of course bow to your superior experience and continue on the way I have always done. Perhaps one day I will bring a smirk to your face when I get it wrong.....

[RatherBeFlying]

In my two glider outlandings, I have had the time and opportunity to pace out my touchdown point at about 100 yards in after a 50' margin over a putative 50' high power line and rollout distance at about 50 yards from a 55 kt. approach.

This gives me a final approach segment of a 1:3 slope or 18 degrees. As that 100' is an estimate, I can postulate being as low as 75' which would yield a 1:4 slope or about 13 degrees.

Note that these slopes are considerably steeper than your standard 3 degree ILS.

Gusty conditions normally come with strong winds; so, a 3 degree approach can get you low well before getting to the runway and you may well find yourself needing considerable power to get back up to a safe glideslope.

Of course, if you are conducting an ILS approach, you do have the advantage of a properly surveyed approach area, but most rural runways without instrument approaches tend to have trees, powerlines etc. in much closer proximity to the threshold.

Also a 3 degree approach will dump you short of the threshold if the engine quits.

As for speeds, remember that they are based on gross weight. After a few hours of fuel has burned off, the approach speed can be corrected by the factor:

sqrt(landing weight) / sqrt(gross weight)

You may already be adding 3-5 kt. to the proper approach speed and this can definitely influence the float in a low wing a/c.

Just before entering ground effect can be a good time to get rid of some of that added speed for gusts, provided that the gustiness has reduced.

Flaps can reduce aileron control, which is why reduced flaps can work better in some a/c.

Stronger gusts and crosswinds are something you have to work up to in a controlled fashion. Recency in strong winds in type counts for quite a bit. If I've been away from flying a particular a/c for a while, my next few flights will be in gentler conditions.

[Flying Binghi]

For the inexperienced -

A stall on short final has a far higher fatal probability then a landing over run.

In gusty conditions, a slightly faster then normal approch speed gives the opportunity to feel the air for the unexpected - and go around if you don't like it.

Refer to your instructer for guidence about the aircraft you fly.

[HappyJack260]

I was landing my Pitts S-2C the other week during an aerobatics contest. The windsock was showing about 30kts + (made flying within the aerobatic box at probably rather higher winds quite interesting).

The way I've been taught to land is to nail the glideslope and attitude, then adjust with power. In the Pitts you don't really have much time to keep looking at the ASI after turning onto finals and you can't see much of the runway either. The trouble is that, to maintain a given glideslope into wind, you need to adjust with throttle, but this makes the approach speed faster. If you just nail the airspeed, you end up with a very steep descent.

So on one approach, I've come in at the right airspeed, flare at the right height, and look out to the side in the flare to judge my height. Relative to the runway, it feels like I'm high and very slow. Which if kept things going would probably mean I'd have a groundspeed of around 40kts instead of 70 kts, manage a 50m landing roll and be stopped in record time.

Instead, I convince myself that I'm about to drop like a stone and bounce like a superball. So I put the power on and go around without even touching. It took me most of the weekend and half a dozen approaches to manage a consistently decent landing...

[gasax]

Welcome to the hovering landing.

On the top of my strip the wind speed is usually higher (big round topped hill). So if you aim for the apex of the hill your ground speed can get into single figures. Controlling height with power suddenly makes a lot of sense.

On the other hand aiming for the threshold puts you into serious turbulence and occasionally some wind rotor - definitely to be avoided.

If I could find a way to taxi to and from the strip in high winds then I guess VTOL would be possible.

[flyme273]

Mungo Man

Error in maths well spotted (I rushed the mail as the canteen was closing, halfway down in the elevator I realised I had goofed – was hoping no-one would spot it).

I concur with your approach (pun ) a nominal increase aids comfort and makes the task easier. However you do not mention any preferred flap settings?

My Flight Manual states:
for normal approach: flaps “as required” speed 75 kts
final flaps 30 deg 65 kts
final flaps retracted 70kts
crosswind: flaps in minimum extended position required for nature of airfield, airspeed not stated.

Perhaps a little vague? or open to various interpretations?

Reduced flap would imply more speed, so its all within the Flight Manual recommendations.

[gcolyer]

Well I managed landing at Perterborough Conington this morning with no problems. The wind was 31018G25 landing runway 28. It was pretty bumby all the way down the glideslope. This time I used Bose-X's advice and pegged the numbers all the way down, which worked fine other than the stall warner screaming everytime i got bumped.

The return flight looks like it will be even more bumpy as the winds have picked up an extra 10kts

[Mungo Man]

There is no way I would want to be whistling along the runway at barton in a cherokee at an IAS of 75kts regardless of the headwind component at 10m......

As has been pointed out several times in this thread, the additions work fine for large aircraft on large runways, on a small aircraft the type of increases you are talking about are massive increases over POH values.

Well, you wouldn't want to maintain appraoch speed until you are over the runway, that would be foolish.

Not all 'large' runways are large when you are flying an airliner. Some of the runways I use at work may look big but are actually relatively small for the aircraft size. Nonetheless we still add up to 20 kts to the approach speed if we need to. However, we must slow down and touchdown at the given Vref for the weight in the touchdown zone. So regardless of approach speed it is still imperative that we touchdown in the right place at the correct speed. I am told to aim to reach Vref at 50ft, which should be when I cross the start of the runway.

Perhaps the reason why airline pilots often struggle with a return to light aviation after a period away.............

Just because we land on 'big' runways doesn't mean we can't control speed.

At the end of the day you can approach flat out in a C152 as long as you slow down at some point and land on the numbers at or near to the stall speed.

[whitehorse]

Whitehorse

Interesting thread. Just got back to base after fighting 60kts mean wind to G75kt winds 30degrees off the the runway, no we didn't land! As a professional pilot flying DHC7´s (C172 on steroids) and an FI in the UK, my experience for what its worth is this;

1. I agree with Mungo Man, the SEP pilot should not go down the ½ headwind plus gust speed. In my experience most pilots end up with a threshold speed which is too high and therefore the landing distance is too long due to the float.

My company has changed the procedures from the above to just following the laid down speeds for the different flap limiting speeds and working the throttles.

2. I agree with Bosse X that the aircraft should be at threshold speed at the threshold.

3. I agree with DFC, if you don't like it go somewhere else.

In my humble opinion a light aircraft pilot should not use trail flap in gusty conditions, what those gust limits might be depends on the experience of the pilot.

I teach plus 5kts on approach but nail the threshold speed. Making sure that there is not too much friction on the throttle.

Don't forget the breaking action. Landing on wet grass etc is going to effect what happens when you are on the runway if there is a crosswind as well.

I don't want to change the thread but in my opinion the weather is not as stable as it once was with gusty conditions becoming more more of an issue.