X-wind landings - flapless?

[Red Leader]

What do people think of intentionally landing flapless in a strong X-wind, especially with fowler flaps?
I just tried it in a C152 and due to a strong headwind component too, and the higher nose attitude of a flapless, I touched down on the tail first!
Mind you, that's what the tie-down ring on the tail is really for, isn't it?

[The Scarlet Pimpernel]

Red Leader....I've not practiced in the light aircraft scene for some time now, but why would you contemplate landing flapless anyway? Perhaps I'm being dull, but the CL/alpha curves don't advise it regardless of any high wing/crosswind/yaw problems your aircraft may encounter.
I'm sorry mate, but it doesn't matter what flaps your ac has (fowlers, zap, etc...) if you're not going to use them what's the difference?? Just add the requisite ergs on to compensate for the lack of lift and accept that you'll land long!!!

[NZ445]

The ability to maintain directional control about the normal axis (Yaw) is the limiting factor for X-wind landings. Although it may be easy enough to keep the aircraft aligned with the runway during the round-out and landing, as the airspeed decreases, rudder effectiveness will reduce and it may be difficult to prevent weathercocking. Therefore, as the X wind component increases, the amount of flap used for landing is normally reduced. This reduces the surface area on which the X wind can act after landing and therefore improves directional control.

Fowler flaps increase your wind area therefore more likely to have that effect of your aircraft. Note I said 'reduced flap setting' not flapless.

It depends of the situation at the time and the aircraft type your flying. Just note the with a nose wheel type aircraft directional control is much easier to maintain on ground than a tail wheel aircraft due to its inherent stability.

Hope this helps!

------------------
Yaw Dampers. Don't leave home without it!

[This message has been edited by NZ445 (edited 07 January 2000).]

[Red Leader]

Thanks to NZ445 for explaining the reasoning behind using less flap so clearly (and better than I was about to).
But The Scarlet Pimpernel reminds us that the flaps are there for good reason and that without them airspeed needs to be increased not just at the flare but also at touchdown, otherwise you may get the problem I encountered.
So it's probably a good idea to keep a reasonable amount of flap on.
I was taught to keep 20F on a C152, but had heard suggestions of using none, and this had worked well before when I kept the airspeed up. However, I will be sticking to 20F from now on.
Thanks for your input folks.

[Charlie Foxtrot India]

Having flaps down will create a larger lift envelope over the inboard of the wing than the outboard, which can contribute to difficulty with directional control in strong winds. Reduced flap settings will lessen this effect.

------------------

[The Scarlet Pimpernel]

I absolutely agree to everything that has been said...I'm just used to full span flap which is a luxury that most ac don't have. I couldn't comment on other techniques, but I have to say that this is the first instance I've ever heard of reducing flap on finals. I guess you keep on living and learning in this game!

[mickg]

On a conentional a/c, flapless landings generally mean a higher threshold speed and, of course, a lot less drag. Therefore, there will be a tendency to float at the flare - not advised during a x wind landing. Your judgement will have to be spot on. Use your flaps!

[4dogs]

Folks,

Full span flaps aside, my understanding of the advantage of landing with less flap in strong X-winds and gusts was that the gust response of the wing was reduced, thus reducing undesirable flight path excursions that may exceed the capability of the normal control surfaces to correct. The penalty in terms of longer landing distance is a trade-off that must be assessed at the time.

------------------
Stay Alive,

[email protected]

[flying among the weeds]

All depends how much runway you have I guess, I seem to remember being taught a reduced flap approach for strong X-winds, not sure that it makes that much difference, at least if you have to reduce flap to handle the X-wind you would be at the ragged edge :)

[Dan Winterland]

CFI, lowering flaps and moving the lateral pressure distribution inboards actually reduces lateral stability, therefore making the aircraft more responsive in roll.

If you need the roll response, put the flaps all the way down.

[mustafagander]

I wonder what the POH has to say on this subject???
What flap has to do with weathercocking I can't imagine. Keel surface and fin area yes.
As they have said, higher Vat usually means float unless you're in practice with this technique, so stick to the familiar and use flap - maybe 1 notch less if you're concerned.

[Teroc]

Found reducing flap to 20° when in a Cessna 152 during a crosswind helped considerably.... i'd normally use the full 30° but on anything approaching 10kts crosswind i'd stick to 20°...
Just put a target on my back eh ? :)

Teroc

[climbs like a dog]

I normally teach reducing the flap setting used on final when the wind is gusty (head or crosswind). The reasoning behind this, as was taught to me, as mentioned earlier, is to improve gust responsiveness and minimise potential deviation from a stable approach path. I presume people are also factoring half the reported gust to their approach speed too?

------------------
0 to 2000ft in 10 minutes

[prop]

Every one seem sto be really well taught.........WELL done!!!!!!!!!!!!!!

[4dogs]

Mustafa,

It is more about roll response.

The upwind wing is generally in clean air while the downwind wing is never so lucky. Reduced flap is an attempt to moderate the tendency of the upwind wing to generate substantially more lift (more curvature, slight increase in lift curve slope, delayed separation, etc) than its less fortunate partner - the roll away from the wind can upset your otherwise well executed zero-drift touchdown and smoothly controlled roll-out. You can't change the theoretical wing loading but you can influence the symptoms.

------------------
Stay Alive,

[email protected]

[Hudson]

No need to factor headwind components or half the gusts or whatever in a C150. It is not a jet where you need to increase speed to counteract for lull in wind. You have a prop will give instant lift for any airspeed drop. With only 5 knots difference in stall speed between full flap and no flap (C152), it makes little difference if you land in a cross-wind with full flap or flapless. Just remember that you will float a lot longer with no flap, and if you are landing on wet grass and only a couple of hundred metres of strip, then chances are you will be still skidding on the grass as you go into the ditch.

[Oz_Pilot]

I was taught and teach reduced flap, mainly for the path deviation from gusts. The yaw and lift arguments sound worth exploring.

Hudson, if the grass is that close, a shortfield is warranted wind or not. If it was 15g25, at 1.3Vs with Vs near 50kts... tell you what, you can fly with no gust allowance. I'll keep some on board.

Of course, most places make an absolute rather than proportional allowance on Vs for approach speeds usually around 15kts (?)

[Billy the Kid]

If your qualifyed to fly the type, then you should be able to do a x-wind landing at the AFM demonstrated limit in the normal landing config. If you prang it, with a non-normal config., then the G-men will have no mercy.
The wise airman reads the forecasts before flight and selects alternative runways or landing sites within the aircraft and his own personal limits, before he decides to get airborne.

[StrateandLevel]

Never had any problem landing a C152 with 27 knots accross and full flap. If its gusty you can reduce to 20 degrees.

[climbs like a dog]

Hudson. Why not add a factor for gusts? If the wind is 15kts gusting 25 and you're coming in on a normal 60kt approach you could lose 10kts of airspeed plus associated lift. You'll need much more power to recover because you're on the back end of the L/D curve, whereas if you added a factor for gusts you'd be adding to your safety margins.

Yesterday I was up in a Tomahawk close on x-wind limits and on an approach which was quite turbulent due to rotor from trees. My student was accurately trimmed @ 70kts (the correct speed for the Tomahawk) but the airspeed was fluctuating between 70-65kts but sometimes as low as 60kts; that is, less than 1.3Vs which is hardly safe. We had a better margin when trimmed for 75kts. I appreciate that the Traumahawk is different to a C150/2 but I have experienced similar on the C152.

------------------
0 to 2000ft in 10 minutes