Crosswind Gusts on Landing Into the Wind?

[APenNameAndThatA]

Another day, another learning experience. Yesterday I was landing a C172 at the Gold Coast airport with my instructor. The runway was 32 and the wind was (IIRC) 310 and 17 kts. Gusts were not mentioned in the weather. I thought, "This will be easy, wind straight down the runway", and very little crabbing was required during final. When we were about 10 m in the air, we were suddenly blown about 10 m to the right. Almost exactly the same thing happened half an hour later when I was coming in to land at Archerfield. The wind at Archerfield felt more like 20 or 25, when I got out of the aircraft, rather than 15, FWIW.  

 

If I was at a very narrow strip I suppose I could have been blown into trees. It seems like another good reason to not land on the numbers, because if someone is waiting to line up, you could get blown into them. Does anyone know any meteorological way to know if there are going to be crosswind gusts as opposed to no gusts or gusts from the direction that the wind is supposed to be coming from? Do gusts, or gusts from right angles to the prevailing wind, become more common the stronger the wind is, say, greater than 15 kt? 

Edited June 18, 2021 by APenNameAndThatA

[Blueadventures]

I always plan to land, wheels on after where aircraft are parked close to runway, whenever possible.  (old gliding habit as there were usually gliders parked close by the launch point and would land after them to prevent an ugly veer off into the parked aircraft resulting from a landing incident.

[facthunter]

I think there would be some circular flow involved rather than gusting crosswind.. Little whirlies occur often  You can also get layers mixing and some shear. Having a SW near a NS beach you can often get what you got especially if the day is warming up .Nev

Edited June 18, 2021 by facthunter

[cscotthendry]

Thermals can account for these gusts on relatively calm days. What feels like a crosswind is a thermal off to the side sucking air across the runway.
You felt in a 172. In lighter planes (ULs and LSAs) it can be more pronounced.
In addition, these gusts can catch you out if you don't watch your airspeed close enough. I had one drop my airspeed 10 knots while landing and because I had let the airspeed decay a bit, the drop in airspeed put me into a stall and the left wing started to drop. My aircraft has very benign stall characteristics so I was able to quickly recover with full throttle, and nose down correction. If I had been flying something with critical stall characteristics like one of the scale Spitfires, I probably wouldn't be here today.
Now I monitor my airspeed in the circuit VERY closely.

[facthunter]

Treat the air you fly in as if it's alive. There are times when it feels  as if you could cut it with a knife, it's so still , but those times are relatively rare. Any wind near the ground is affected by the surface as it's not freestream any more. Surface heating affects it as well as objects on the surface. (Trees sheds etc. Thermally days are generally rough till you get above the transition layer.

     In relatively still air the heated runway surface can deprive you of lift as you  "arrive" over the end of it also.. Nev

[APenNameAndThatA]

The POH of the Foxbat says to land flapless if  the wind is over 16kt. I used to think of that as just being a cross wind thing. Now, I will think of it as any wind. 

 

I can see more why instructors are said to add a few kts to the book as a safety factor, even if it is a bad idea. Your speed has to decay somewhere, so it might as well be a foot off the ground, (even if it takes longer because ground effect decreases your drag). 

 

Thank you for the comments about thermals and eddies. 

[cscotthendry]

9 minutes ago, APenNameAndThatA said:

I can see more why instructors are said to add a few kts to the book as a safety factor, even if it is a bad idea. Your speed has to decay somewhere, so it might as well be a foot off the ground, (even if it takes longer because ground effect decreases your drag). 

 

 

That is what I do now. I do have the luxury of long enough runways to do that. It may not be feasible for short field landings, but I avoid those when I can.

"Your speed has to decay somewhere, so it might as well be a foot off the ground,"

Agree totally ... up to the point you're in danger of running out of runway. But then there is the GoAround option.

[skippydiesel]

I was trained to be able to do partial flap/no flap landings, just in case. It is important to be able to judge what is a normal attitude with different stages of/nil flap.

 

As for ground effect - a very useful technique for reducing ground effect is to lift/stow all flap. There is an immediate loss of lift, so this should only be done when you are almost on the ground - very useful in short field landings, as wheel brakes come into effect erly, assisting with short ground role.

 

 

[facthunter]

Even big stuff allows for wind. BUT the wind is a smaller % of a planes target threshold speed if it stalls at over 100 knots, A pretty useful formula is ALL the gust and 1/2 the headwind component. . YOUR stall speed also varies with actual weight and Cof G position. Dumping flap will put more weight on the mainwheels with a tricycle gear but don't muck things up  doing it. Ground spoilers are much better when you have them..Flaps have drag if you are still airborne. Nev

[APenNameAndThatA]

2 hours ago, facthunter said:

Even big stuff allows for wind. BUT the wind is a smaller % of a planes target threshold speed if it stalls at over 100 knots, A pretty useful formula is ALL the gust and 1/2 the headwind component. . YOUR stall speed also varies with actual weight and Cof G position. Dumping flap will put more weight on the mainwheels with a tricycle gear but don't muck things up  doing it. Ground spoilers are much better when you have them..Flaps have drag if you are still airborne. Nev

That’s a lot more than I was told - just half the gust! 

[Thruster88]

I think we need to do some maths on this landing. If the 172 was in a steady 10knot crosswind without any pilot correction it would be moving sideways at 5m per sec, so 2 seconds to deviate the 10m.

 

If we do a myth busters type experiment were our cessna is mounted on a frictionless rail and subjected to a 10knot crosswind it would take 4 seconds to deviate 10m assuming it was able to accelerate to 10knots at the end of the 10m travel, unlikely. 

 

In 4 seconds the 172 on approach in the 17knot wind would cover about 110m. Would a sustained 10knot crosswind gust be possible in this situation,  I think it unlikely however it could have happened. My probable cause for the deviation, the pilot failed to apply correct and timely control input. I know it sounds harsh but I hope you take it in the spirit it is intended. 

 

In my private flying career I have done a lot of low level farm crop inspection type flying in a very light tail wheel thruster aircraft. Flying down tram tracks looking for weeds, slipping between the tracks 3m apart as quickly as possible just for fun. Flying down wind of a tree line like in the picture to feel the turbulence. Landing on narrow farm tracks. Doing down wind turns to experience the Visual illusion. Thousands of tail wheel landings. Has the wind ever moved me, no. Coming in to land now I feel very comfortable, I fly the aircraft. Always landing on and maintaining the centre line is satisfying. I am sorry if I sound like an a dick. Everyone should get a tail wheel endorsement, it will teach you about small timely control inputs. The Cessna 172 that I got my ppl in was destroyed by a "gust of wind". https://www.atsb.gov.au/publications/investigation_reports/1998/aair/199800049/

 

Never stop learning.  

 

[APenNameAndThatA]

On 20/06/2021 at 8:17 AM, Thruster88 said:

I think we need to do some maths on this landing. If the 172 was in a steady 10knot crosswind without any pilot correction it would be moving sideways at 5m per sec, so 2 seconds to deviate the 10m.

 

If we do a myth busters type experiment were our cessna is mounted on a frictionless rail and subjected to a 10knot crosswind it would take 4 seconds to deviate 10m assuming it was able to accelerate to 10knots at the end of the 10m travel, unlikely. 

 

In 4 seconds the 172 on approach in the 17knot wind would cover about 110m. Would a sustained 10knot crosswind gust be possible in this situation,  I think it unlikely however it could have happened. My probable cause for the deviation, the pilot failed to apply correct and timely control input. I know it sounds harsh but I hope you take it in the spirit it is intended. 

 

In my private flying career I have done a lot of low level farm crop inspection type flying in a very light tail wheel thruster aircraft. Flying down tram tracks looking for weeds, slipping between the tracks 3m apart as quickly as possible just for fun. Flying down wind of a tree line like in the picture to feel the turbulence. Landing on narrow farm tracks. Doing down wind turns to experience the Visual illusion. Thousands of tail wheel landings. Has the wind ever moved me, no. Coming in to land now I feel very comfortable, I fly the aircraft. Always landing on and maintaining the centre line is satisfying. I am sorry if I sound like an a dick. Everyone should get a tail wheel endorsement, it will teach you about small timely control inputs. The Cessna 172 that I got my ppl in was destroyed by a "gust of wind". https://www.atsb.gov.au/publications/investigation_reports/1998/aair/199800049/

 

Never stop learning.  

 

I don’t mind your comment in the least. I am actually grateful for it (really). One of the few benefits of being older is that I enthusiastically mention the mistakes I make, and ask him to make a mental not of them fir later. It was not a easy habit to get into. 

 

One instructor accused me of over controlling when I was sitting out a gust in cruise. And a few minutes before had told me to look on a map to find the hills that were 3500 ft high in front of us. They were 2500 ft but looked higher because that’s that they do. I did get shitty at him.  

 

The aircraft stayed wings level and was pointing pretty much straight ahead, so I’m not sure what control input would have caused that. (I would have expected to weathercock into a gust.) I could easily have taken four seconds to respond, as I was taken by surprise. It would have taken a while for the gust to accelerate the plane.

 

On a side note, with the accident report you mentioned that the pilot used aileron and did not mention pushing the yoke forward. One of my pet hates with instructing is that the tell people that if you pull back on the stick, the aircraft climbs. (Not an original pet hate, but I came up with it myself.)

 

I will quiz the instructor about my control inputs. They are as good as my other instructor who was a training captain in an airline. 

[Student Pilot]

A lot of overthinking going on. Just fly the aircraft..........

[facthunter]

Some people do make their own turbulence. A night on the turps helps. Nev

[APenNameAndThatA]

2 hours ago, Student Pilot said:

A lot of overthinking going on. Just fly the aircraft..........

I completely disagree. a) How can it be overthinking to wonder why you ended up beside the runway and not over it?  b) Thinking about why you ended up over the grass instead of over the runway is part of the fun of flying. 

 

When you say that there is overthinking, are you suggesting that thinking about how come the aircraft ended up in the wrong spot is actually harmful? 

[poteroo]

Whatever the wind, pilots face a dynamic situation which differs with airport surrounds. AWS is only for your guidance, and all pilots need to get out and learn how to manage the weather from cues that exist at the time of operation.  The humble windsock can provide a lot of info - but it's little help if you fly straight-in approaches, or cut into the circuit on base, and lower than 1000agl to boot.

 

If you fly directly over the windsock which is relevant to the into the most into wind strip, you should be able to observe the lateral sock swing. The greater this is, and the speed at which it happens, will help you to judge the possible cross-wind variation.  Then, as you fly the circuit, or if you very sensibly fly an upwind, (ie, slower g/s), leg, you should be able to note the up/down sock movement, and the speed of that. This vertical 'flapping' will help you to anticipate the gustiness to expect in the flare.  Of course, there are other cues that you should seek out, such as waves on dams, tree movements, dust movements, and the 'ripple' effect of wind passing over older crops and ungrazed country.  Your instructor should be teaching you all this stuff during your navexs.

 

Managing wind and low level turbulence is helped by a pilot learning to fly the aircraft intuitively and always in balance - but with eyes outside and brain engaged.  Again, don't expect to be crosswind competent until you can manage in flight turbulence, at normal approach speeds, without fixating on instruments.  You have to use your feet, hands, eyes and brain to keep the aircraft in the required attitude and approach position - without getting yourself into a high risk out-of-balance situation.  Until a pilot can fly in balance - how on earth can we expect them to be able to employ çross-control' techniques to offset crosswinds?  It needs good instruction and lots of practice.

 

happy days,

[facthunter]

Ignorance is what makes things more difficult.. even impossible sometimes. Your plane is never on rails..IF the air is moving, you move with it. You cant be expected to do things you haven't been shown or you have never even thought about. 110 years ago planes couldn't handle other than very light winds.. Nev

[APenNameAndThatA]

2 hours ago, poteroo said:

Whatever the wind, pilots face a dynamic situation which differs with airport surrounds. AWS is only for your guidance, and all pilots need to get out and learn how to manage the weather from cues that exist at the time of operation.  The humble windsock can provide a lot of info - but it's little help if you fly straight-in approaches, or cut into the circuit on base, and lower than 1000agl to boot.

 

If you fly directly over the windsock which is relevant to the into the most into wind strip, you should be able to observe the lateral sock swing. The greater this is, and the speed at which it happens, will help you to judge the possible cross-wind variation.  Then, as you fly the circuit, or if you very sensibly fly an upwind, (ie, slower g/s), leg, you should be able to note the up/down sock movement, and the speed of that. This vertical 'flapping' will help you to anticipate the gustiness to expect in the flare.  Of course, there are other cues that you should seek out, such as waves on dams, tree movements, dust movements, and the 'ripple' effect of wind passing over older crops and ungrazed country.  Your instructor should be teaching you all this stuff during your navexs.

 

Managing wind and low level turbulence is helped by a pilot learning to fly the aircraft intuitively and always in balance - but with eyes outside and brain engaged.  Again, don't expect to be crosswind competent until you can manage in flight turbulence, at normal approach speeds, without fixating on instruments.  You have to use your feet, hands, eyes and brain to keep the aircraft in the required attitude and approach position - without getting yourself into a high risk out-of-balance situation.  Until a pilot can fly in balance - how on earth can we expect them to be able to employ çross-control' techniques to offset crosswinds?  It needs good instruction and lots of practice.

 

happy days,

Looking at the windsock over time is a good idea. Again, there was very little to no movement on final until late. 

[facthunter]

For little planes a sock at the end is more value. A dust devil might only be 80 metres wide and have no dust if there's grass..  Nev

[Thruster88]

31 minutes ago, APenNameAndThatA said:

Looking at the windsock over time is a good idea. Again, there was very little to no movement on final until late. 

Just don't look at that windsock for to long though. We are constantly told to avoid distractions like traffic screens and EFB's that reduce our see and avoid responsibility. That is sarcasm btw.

 

Poteroo's first sentence sums it up nicely. Regardless of the wind information we have obtained we are in a dynamic situation and need to apply appropriate control inputs constantly. A dust devil will not show on a windsock unless it is really close by. I have intentionally flown through visible dust devil's. it is a short sharp jolt, I am sure everyone who has flown for any time has hit them. They are often about but rarely seen if there is no dust ash on the ground.

[Old Koreelah]

1 hour ago, facthunter said:

For little planes a sock at the end is more value. A dust devil might only be 80 metres wide and have no dust if there's grass..  Nev

The sock is usually near the centre of most airports, so it might be far off and hard to see during your final approach. Another reason to have a bit of reserve energy up your sleeve in case of unseen wind gusts.

[Bruce Tuncks]

If you look up stuff on wind gusts as written for wind energy turbines, you may see it claimed that the strongest gusts are 15 degrees off the main direction. This is clearly because of the thermals mentioned before.

The only advice I can offer is to expect side-gusting on a windy day. At least, near the ground, the vertical motions of the gusting are no longer there.Imagine how hard it would be to try and land on a mesh runway at 2000 ft.

[Student Pilot]

On 21/06/2021 at 7:15 PM, APenNameAndThatA said:

 When you say that there is overthinking, are you suggesting that thinking about how come the aircraft ended up in the wrong spot is actually harmful? 

No I'm suggesting fly the aircraft, keep it straight if it deviates put it back on line. When it happens again you will be aware. If the conditions are beyond your skill level, don't fly.  

[APenNameAndThatA]

2 hours ago, Bruce Tuncks said:

If you look up stuff on wind gusts as written for wind energy turbines, you may see it claimed that the strongest gusts are 15 degrees off the main direction. This is clearly because of the thermals mentioned before.

The only advice I can offer is to expect side-gusting on a windy day. At least, near the ground, the vertical motions of the gusting are no longer there.Imagine how hard it would be to try and land on a mesh runway at 2000 ft.

I'm no meteorologist, but are you sure that it is not to do with the how much wind veers (moves to clockwise) when you get close to the ground? In other words, are you sure that it is not due to wind usually going at right angles to the pressure differential except when close to the ground? Maybe gusts act more like higher-up winds. 

 

Sin of 15° is about 0.25. So maybe you could expect a 20 kt wind to automatically have a 5 to 7 kt crosswind component with gusts. 

[APenNameAndThatA]

1 hour ago, Student Pilot said:

No I'm suggesting fly the aircraft, keep it straight if it deviates put it back on line. When it happens again you will be aware. If the conditions are beyond your skill level, don't fly.  

Got it. I was with my instructor.