Flying and gusts

[gantshill]

I have a question about flying when there are gusts. I'm a low hours pilot. I realise individual pilots have their own thresholds and limitations about what is and isn't acceptable flying weather. One must also be prepared for actual weather being worse than forecast. When it comes to wind, I've tended to avoid gusts, even if it is blowing straight down the runway, as the fear is that as the gust comes and goes (by their very nature), then an aircraft on finals might experience sudden losses of lift quite low to the ground. I suspect wind shear might be a problem too? So I just wondered what the more educated and experienced pilots think about flying with gusty weather? Do you avoid it? Any hairy moments? Other than increasing approach speed and changes in aircraft configuration, what else do you do to mitigate against the gusts?

[tmmorris]

Number 1: always be prepared to go around.

With that in mind, you can start to gradually expand your comfort zone (I'd start with gusts straight down the runway) within of course any limitations in the POH (and for now, I'd stick to demonstrated crosswind, too). At some point you will realise you have exceeded your current comfort zone and can set a (temporary?) limit until you feel ready to do expand again.

And don't forget that (especially in some types) taxying can be at least as hazardous as takeoff and landing...

[Pace]

Normally we talk about adding half the gust factor on the approach. I question that because on the approach its likely that the winds will be stronger than the reference point on the airfield.

Wind speed and direction maybe different.

We had a thread on crosswinds and rudder authority is required to maintain the centreline as well as control over landing.

It therefore stands that in very strong crosswinds you look at a different technique to landing at or near the stall but use a slightly higher speed for extra control and fly it on.

There are other considerations like the headwind component and runway length.
I have experienced + and - 25 to 30 KTS with shear so trundling down at VREF would be none to clever and speed management as well as reducing speed comes into play in those conditions.

Energy is your friend but you have to be able to control it

Pace

[Chesty Morgan]

Originally Posted by Pace

Wind speed and direction maybe different.

That's why you bleed the headwind/gust factor off over the threshold.

[Pace]

That's why you bleed the headwind/gust factor off over the threshold

It was a warning that some pilots will take the given surface wind and gust factor and use that on the approach which may not be enough for the shear experienced at 500 or 1000 feet
obviously you have to come back to a determined speed on landing

We also have to consider the 1.3 times the stall in a given configuration. That is a figure that should give enough energy with a closed throttle to transition from a descent profile to the flare so that you touchdown at or near the stall. Important for published stopping distance

If you fly the aircraft on then you could fly on with a speed with a greater margin over the stall and effectively have more control authority and more residual energy above the stall for surface shear

Flying on is far easier with an aircraft with a greater distance between the nose wheel and mains as a few degrees pitch will keep the nose wheel clear

I often refer to a Citation incident at Edinburgh where a Pilot I know who had control problems who touched down and successfully stopped with I believe tyres intact at a radar estimated 193KTS, 100KTS above the normal landing speed and above the tyre limiting speeds.
I place this to show how little relevance the stall is to landing an aircraft other than the obvious shortest landing distance etc
An extreme example maybe but just to make a point

https://assets.digital.cabinet-offic...JBIZ_01-10.pdf

Pace

[mary meagher]

ah yes. As tmmorris says, taxying may be as hazardous as takeoff or landing; (especially in sensitive taildraggers)...but the tradeoff is that your accident when taxying will be at a much slower speed....as I found in Ireland. Tail in the air, and stuck in the mud. When the crosswind gust struck I was far too slow to go around, say 5 mph. Good news was no damage at all at all!

As others here advise, an increase in approach speed is called for in gusty conditions. Or you may simply declare, as I do these days, "sorry, I changed my mind about flying today. The conditions exceed my personal limitations."

Another suggestion, if you are already airborne in a sensitive taildragger and you are not happy with that crosswind runway in use, if you ask them nicely they may offer you ANOTHER RUNWAY more into wind. (or if you have enough fuel on board, go someplace else)

[fireflybob]

Perhaps we should also comment that the definition of a gust is 10 knots or more from the mean wind speed.

The wind passed by ATC should be the average over the previous 2 minutes. I say this with all respect but minor airfields are rarely equipped with an averaging device and/or a bespoke aviation anemometer which is suitably sited. This means that wind readouts at these airfields are no more than advisory and of course there can be a significant difference between the reported wind and actual wind at near the landing threshold.

To some extent the wind is always varying but in terms of aircraft control during take off and landing it's the degree of variability that matters.

[soay]

Adding half the gust factor is all very well, but some aircraft float along in ground effect if you do that and the timing of the gust is wrong. This leaves them much harder to control in a crosswind. What's the best advice for those types?

[rnzoli]

Also a low hour pilot here and I have these in mind:
- I don't deliberately look for gusty conditions, the gusty conditions find me anyway
- no passengers on board in known gust conditions nearing my personal demonstrated limits
- extra fuel on board for alternatives or multiple landing attempts
- one challenge at a time: intended runway should be sufficiently wide and long enough to be considered easy for normal weather
- first approach is always a teaser, just to see how much I can keep it stabilized, and I may actually land also, but that's just a bonus
- manifold pressure not lower than 10 HgIn, so that the engine will respond faster for my quick throttle advance in sheer panic
- cameleon eyes - one eye glued to airspeed indicator, while the other does the regular work (= quick glances between the instruments and outside view)
- my approach profile is more shallow, with higher power setting and speed till the threshold, then I do a pre-flare after passing the threshold, to bleed off the excess (AIR!)speed, then I let it down firmly with only a short flare (some call that an "arrival", not a "landing", but a safe arrival is my preference over a nice landing attempt resulting in a runway excursion)
- maximum patience and absolutely NO pressure to land, if I need 2-3 circuits, it's all fine, as long as the approaches are getting better - the wind might be giving me a break during one of my attempts and let me land nice and smooth.

So far it worked.

[Jonzarno]

quick throttle advance in sheer panic

I know you probably don't mean this literally, and I don't know what aircraft you fly, but this is definitely not a good habit to get into.

On higher powered SEPs, banging the throttle open like that can induce yaw and roll that can result in an accident.

[john_tullamarine]

Normally we talk about adding half the gust factor on the approach


That's why you bleed the headwind/gust factor off over the threshold.


This sort of consideration generally is the province of the heavy metal brigade.


.. in which case, the story is


(a) half the steady wind and all the gust to a suitable maximum (20kts or so)


(b) bleed off the steady wind additive but maintain the gust additive


Reason for the difference is


(a) steady wind has a reasonably predictable reduction near the ground


(b) gust is totally random.


A variety of discussions in Tech Log, eg, http://www.pprune.org/tech-log/10456...ment-vref.html

[rnzoli]

Originally Posted by Jonzarno

I know you probably don't mean this literally, and I don't know what aircraft you fly, but this is definitely not a good habit to get into.

On higher powered SEPs, banging the throttle open like that can induce yaw and roll that can result in an accident.

Fully agree, I wrote the "panic" part only for a bit of self-mockery.

Also the same goes for drastic attitude oscillation, i.e., trying push down the nose first and then yanking up the nose in a go-around is a big no-no.

So it really helps me and probably everyone less experienced, if we prepare mentally for a planned go-around, rather than a landing, because we will handle the throttle, rudder carb heat, stick, flaps, etc. smoothly.

[Armchairflyer]

quick throttle advance in sheer panic

I know you probably don't mean this literally, and I don't know what aircraft you fly, but this is definitely not a good habit to get into. On higher powered SEPs, banging the throttle open like that can induce yaw and roll that can result in an accident

Apart from that, it would also be an abysmal way to treat an aircraft engine. AFAIK they are not designed for sudden large power changes. Might be not as serious for Rotax engines, but the POH of one IO-390-powered club aircraft explicitly warns about abruptly increasing or reducing power as a rather reliable way to damage the engine.

(Not directed at rnzoli, but it appears that several SEP pilots are not aware of this. In my even more beginner days, I wasn't really either.)

[Pace]

Adding half the gust factor is all very well, but some aircraft float along in ground effect

Soay

That is a technique problem not a speed problem hence why I posted that extreme link above to make a point.

We have it drummed into us that landing an aircraft is all about pulling back and back till the aircraft sinks onto the Tarmac, that we should be at a speed near the stall speed but that is far from the truth.

Yes that is a technique used in the majority of especially PPL flying but in strong winds gust and shear the last thing you want to be doing is hanging at 10 feet trying to get the perfect touchdown at or near the stall. In that state you will have little control authority and will be at the mercy of crosswinds or shear

sometimes you need to fly the aircraft on bang it on call it what you want and sometimes at a higher speed away from the stall winds and runway length taken into consideration

Pace

[Piltdown Man]

You should be capable of flying in nasty weather. Whether or not you do so is up to you, but you need to get the confidence to enable you to do so. The first thing to do is read your aircraft's operating handbook. And by that I mean the real thing published by the manufacturer for your specific type and version, not something that an amateur at the aero club has knocked up. It will give you an approach speed range or the method for working one out.

I'm going to assume you are not in a mountainous area. Things can be slightly different here.

The basic guts of approach speeds is that your airspeed indicator will give you a clue as to your stall speed (at max. weight, forward CofG) with maximum landing flaps; it's the bottom of the white arc. To that add one third. Many light aircraft stall in landing configuratuon at about 45 knots. This would imply an increment 15 knots giving an approach speed of 60 knits. To that, add half the gusts. So 15 knots gusting 25 knots means adding 5 knots. And we are talking about headwind here, not crosswind. But if your POH says different, do that!

Now grab an instructor and go and fly with them on a windy day. Have them demo the approach speed, power and attitude. Now try yourself. Do not add more speed. Faster is not safer, just as slower is not safer. Also remember that the numbers from the book are at maximum weight with most forward CofG. So if you fly at book speeds, you still might be too fast. Some suggest reducing your approach increment by 10% for every 20% of weight you are below your max. landing weight.

At higher levels, 1,000' down to 500' you will have sufficient height to control your speed. You do not need extra speed. Control your speed with pitch, power and attitude. You will have to work during approaches in gusty weather and providing you make timely corrections you will not fall out if the sky. As you approach 50 feet above the ground, bleed your speed off and land normally on the mains. Throw away any approach you are not happy with, go around and try again.

The skill will come, but it does need practice.

Best of luck,

PM


PS. I used to live round the corner from Gants Hill in Blenheim Avenue. Small world.

[Piltdown Man]

Answering your specific questions:

In very gusty weather I generally use less flap.

I add the increments to Vref. as specified in the aircraft's AOM and no more (maximum increment = 20 kts).

I work harder.

I go for a touchdown in the TDZ, on the centre-line from a stabilised approach at Vref.

I personally get to do 250 landings a year (my colleagues do the other 250) and do one or two go-arounds because I'm not happy with the approach.

On a previous type I flew with the airbrake open to spool the engine up. It also appeared to improve speed stability.

Probably not relevant to you but on some approaches I disconnect or at least over-power the auto-throttle due to its lag and very binary nature.

Some of the landings are not very pretty and some of the approaches are very rough. But that's life.

PM

[Pace]

PM

You touch on an important part which is go arounds and how many hang on for grim death when it all goes pear shaped usually coming to a not very pretty stop with just bruised egos.

Especially in rough weather a go around should be predominant in your thoughts on the approach rather than something you think about when its all going wrong.
In such weather its better to expect a go around and be prepared for it rather than expecting to land and not being prepared to go around.

You should be as comfortable going around even from touchdown as you are at landing although I suspect some are not really that comfortable with either

Pace

[gantshill]

Thanks for all these great and helpful responses. Alas it was largely winds aloft that kept me grounded today, it all looked like far too much hard work all round!

[Pace]

G

You state you are a low experienced pilot then asked how experienced pilots deal with gusts and windshear?
It is always important to fly with what you are comfortable with! The thread like most threads expands into discussion and maybe away from the novice pilot.
So just to confirm always fly within your own limits and the aircraft limits and if it's not right for you fly another day ))

Pace

[Jonzarno]

Exactly right. And remember: "If there's any doubt, there is no doubt"!