The inboard stall strips are merely to ensure that the wing stalls from the root outwards.

liam, you didn't specify which version of the PA28 your speeds are for - they are significantly different for different versions - Cherokee, Warrior, Archer, Arrow II, Arrow IV, Arrow IVT, Dakota...?

What a mess!

I was reading this thread from the beginning and not until the last post (Captain Stable) it was mentioned the importance of stating what type of PA28 you are talking about.

Some people are referring to PA28 as it was one model. You should know better if you are going to post such important things as landing speeds.

The original question didn't state what model of PA28 to refer to either. I know my personal flapless speeds for a 140 and a 161, just tell me wich one you are interested in.

Capt Stable

The stall strips ensure that the outer wings generate lift, when the inner wings have reduced or no lift, thus assisting lateral stability (and providing effective ailerons)

What would happen if the outer wing stalled first?

What happens if you take flaps and increase the lift in the inner wing section?

Reduced lateral stability.


Intercepted

Why don't you read the original question again? The OP wishes to know the incremental landing distance, not the approach speed.

The type of PA28 is irrelevant, because this data is not published in the POH.

I'm not quite sure what you're trying to say here. The inboard stall strips have no effect whatsoever on airflow over the outer sections of the wing, so cannot ensure anything about what they produce. If the outer section of the wing stalled first, you would have significantly reduced lateral stability and therefore pronounced probability of wingdrop close to the stall leading to possible spin. Taking flaps reduces the stall speed by increasing lift and drag at low speeds.

When you say "the inner wings have reduced or no lift" do you mean that the wing is already at the stall?

I stick to what I said earlier - the inboard stall strips are to ensure that, clkose to the stall, it is the inboard sections of the wings that stall first, aiding lateral stability.

Capt Stable

I think we are saying the same thing.

The stall strips cause the inner wings to stall first (producing reduced or no lift), which ensures that the outer wings are still producing lift at the same time, increasing lateral stability, as you say.

Taking flaps does indeed lower the stall speed by increasing lift, but only across the inner sections (where the flaps are), so thinking spanwise, lateral stability is reduced.

Im only using the stall strips as a reverse analogy, not as a direct comparison.

My hypothesis is that taking flaps in gusting crosswinds is (a) good, because it reduces the tendency to float and thus drift in the flare, but (b) bad, as it reduces lateral stability and thus resistance to gusts.

On the other hand, once one gets lower and the wind speed often reduces, I'll take flaps for the erasons Whopity has already outlined.

Hope this makes sense now.

How does having the outer parts of the wings stall first decrease lateral stability? And perhaps more to the point, how does that affect lateral stability when the wings are not stalled, as would hopefully be the case during the final approach and flare? I know having the inner parts stall sooner increases controllability, but I don't know how it increases stability?

Not using flaps allows for a higher approach speed, which increases aileron authority and lateral stability.

I've been thinking along the same lines as Bjornall. Lateral stability is not a function of the distribution of lift left/right/inboard/outboard, but rather a function of how the aircraft reacts to upsets of that distribution, and how easy it is to correct for this.

Along those lines, I would rather have the inboard portion of the wing generate most of the lift. If there is a gust then the resulting moment of roll will be less (moment = arm x force), compared to the situation where the outboard portion would do most of the work. And this means that less opposite moment (aileron input) would be required to keep the aircraft level.

I've experienced that long/slender wing aircraft such as gliders and a DA-40 are harder to fly in gusty conditions compared to short wing aircraft such as an R2160. Then again, there's also a difference in wing loading between these aircraft so their lower stability may not be entirely due to the larger moment generated by the larger wing.

Therein lies the mis-conception about Part M. Its not the maintenance thats gold plated. Its the paperwork trail that is, sometimes to the detriment of the maintenance jobs.:ugh:

I was taught that:

If the inner wings stall first, the pilot can notice an inadvertent stall while he still has aileron authority.

If the outer wings stall first, but not quite simultaneously, a wing can drop (at least the extra leverage makes it more likely).

which made sense to me.

FWIW I go with Whopity on the flapped crosswind approach: get it on the ground and rolling as slowly and as early as possible.

[Uninformed, uneducated speculation=ON]
Given that the main problem in strong crosswinds on landing would be gusts, I agree that having the majority of lift close to the CofG is probably preferable. The main factor, of course, would be whether a gust will lift a wing beyond the capability of aileron to bring it back down again. In a dihedral aircraft like a PA28 this is going to be more of a problem than a plank such as the C152's wing.

I'm not sure whether the lower wing of a PA28 would also cause further problems with more pronounced ground effect than with a high-wing type.

Where that puts us on the question of flaps extended or clean wing for a crosswind landing I have no idea. I can see merit in both sides of the argument - but I'm not an aerodynamicist.
[Uninformed, uneducated speculation=OFF]

In very general terms and without being aircraft specific is it not good practice to have a slightly faster approach speed and possibly fly it clean while flying in gusty conditions on final?

Thats what I thought.

No.





.

ok then. I presume there is no general advice applicable to all aircraft?

Fly it within the POH.

Just a thought, flapless or clean, if you have a strong crosswind (demonstrated limit or above) and you are using the crab method then is it not stupid to aim for a slow speed (near the stall) on touch down. My reasoning is that if, when you kick off the drift, you have not got enough rudder to straighten up and then have to go around then you are relying purely on the engine for acceleration. You are already at a height that does not enable the nose to be lowered without causing you to land, you are also drifting sideways across the runway, either way unless you have bags of power available then it is all going to get rather nasty. Of course the slower you are going the less rudder authority you will have anyway. Always better if possible to use the wing down (in my humble opinion) then at least you can fly it all the way onto the ground and know in advance that you are able to deal with the crosswind.

trex450

I've never had any trouble landing a PA28 (or PA32) in a strong crosswind using the crab method (which my pax said is more comfortable than wing down), using the recommended approach speeds in the POH.

It is an inevitable fact that one will end up flying at slow speed in proximity to the ground during a landing ;)

I have gone around from about 10 feet one particularly gust day and there was no drama, just a nice clean climb away.

I'm pretty sure that there's a certification requirement that the aircraft has to be capable of landing normally with a crosswind component that's x times the stall speed. (x=0.5 or thereabouts?) So you should have sufficient rudder and aileron authority to obtain the required wing down/sideslip attitude, and sufficient ground clearance in that attitude all the way down to the recommended touchdown speed, at the stated *demonstrated* crosswind limit.

Of course if you exceed the limits of the POH, you're a test pilot and all bets are off.

All in a Flap
 

NO! - is very unfair and unhelpful to a genuine question.

From the PA28 Archer 111:

'The gross weight of the Archer 111 with power off and full flaps is 45 KIAS. With flaps up this speed is increased by 5 KIAS'.

'In high winds, particularly in strong cross winds, it may be desirable to approach the ground at higher than normal speeds with partial or no flaps'.

The advantages of flap;

1) They allow a lower nose attitude improving the forward vision at various speeds, particularly useful when approaching to land.

2) Owing to the increased drag they allow a higher power to be used giving to the benefit gained from the increased propwash such as an enhanced fin/rudder, tailplane/elevator and also lift, lift increase is marked with most twin props.

3) Reduced approach speed of 1.3 the stall, owing to reduction in the in the stall speed with flaps deployed.

4) Reduced float during the hold-off

Disadvantages of flap.

1) Owing to the changes in the lift/drag co-efficient the aircraft is less stable in pitch,roll and yaw.

2) Less power over drag is available.

3) less range in pitch owing to the increase in angle of attack induced by flap.

Therefore in normal conditions the benefits of flap are clear but in turbulent conditions greater skill in control is required. To maintain the approach path or should a go-around be required say because of windshear then the ability to resist sink and/or to climb is impaired and requiring greater changes of power.

Is that not what I said above?

.....is it not good practice to have a slightly faster approach speed and possibly fly it clean while flying in gusty conditions on final?

Thats what I thought.

Kinda interesting units of measurement for weight/mass... ;) :confused: