STO, and fast cruise

[lark]

I understand the theory behind it (well some of it) however 5 deg negative didn't seem to make much more than 3-5 kts difference

 

 

[David Isaac]

I understand the theory behind it however 5 deg negative didn't seem to make much more than 3-5 kts difference

In what aircraft type Lark.

The Maule makes very effective use of inverted flap to increase TAS in the cruise.

 

 

[Kyle Communications]

The Just Aircraft Highlander with the superstol wing is what you are close to. Automatically deploying slats depending on airspeed and climb angle also huge flaps and VG's now on the wing make this aircraft ridiculously slow flying yet still will cruise at 90 to 95 knots easily

 

 

 

[David Isaac]

But the Highlander is still limited to around the 90 -95 due the nature of the high loading at speed. The Maule had a cruise in excess of 125 knts from memory and it had a high lift wing but nothing like the highlander. Auto deploying slats is excellent, but it has a weight penalty which is why most STOL ultralights that use slats have fixed slats.

 

That highlander is one VERY impressive STOL performer. I want one LOL

 

 

[cscotthendry]

Bones:

 

I think Douglas did exactly what you suggest on the F8 Crusader

 

http://air.blastmagazine.com/f-8-crusader/

 

Oh, and BTW, I think you need a different avatar. That purple thingy creeps me out big time!

 

 

[biggles5128]

Remember that old italian bloke Bernoulli???, his theory might just answer your question.

 

 

[Guest GraemeM]

Bones:I think Douglas did exactly what you suggest on the F8 Crusader

 

http://air.blastmagazine.com/f-8-crusader/

 

Oh, and BTW, I think you need a different avatar. That purple thingy creeps me out big time!

That's Bones on a good day, you don't want to see a pic of him on a bad day?

 

 

[Guest Maj Millard]

I understand the theory behind it (well some of it) however 5 deg negative didn't seem to make much more than 3-5 kts difference

We

Well even 3-5 kts additional cruise over say a four hour flight is nothing to be sneezed at , especially when it free, and doesn't impact at all on fuel burn..................Maj...

 

 

[metalman]

Interesting thoughts, I would say altering the shape of an airfoil would be fairly simple, building it to handle flight load might be a bit difficult, I'll give this a bit of thought, the main problem I see is having the skins or (preferably) fabric movable enough to allow a new shaped airfoil,

 

 

[lark]

WeWell even 3-5 kts additional cruise over say a four hour flight is nothing to be sneezed at , especially when it free, and doesn't impact at all on fuel burn..................Maj...

Yeah, neg flap is still a good thing, not knocking it at all. Just saying that the speed increase may not be as great as claimed in some cases!

 

 

[lark]

In what aircraft type Lark.

Maule

 

 

[Guest Maj Millard]

Yeah, neg flap is still a good thing, not knocking it at all. Just saying that the speed increase may not be as great as claimed in some cases!

Well yes I would agree that the gain is not huge, in terms of airspeed. However it is a free ride and when you look at the gain over say a years' flying, it is better than boot to the arxx......I first experienced reflex- flap on the Lightwing GA which has it standard with approx 5 deg up on the flaps. On a smooth-air morning flight I steadied the indicated AS at 60 kts with the reflex flap off. I then selected the reflex position and the AS went to 65-66 kts !!.....not really believing this myself I then de- selected it and the AS went back to 60Kts. It does work and on a plane like the GA LW can be a significant gain.................Maj...

 

 

[Thirsty]

The negative flap setting on the CT range of aircraft makes a large difference in speed. Can't recall the exact figures but when you select the negative flap setting you can feel the aircraft accelerate - it's feels like you're adding a fair bit more power. I like it and want to try it on my 160 :)

 

 

[eightyknots]

[ATTACH=full]16660[/ATTACH][ATTACH=full]16658[/ATTACH]The thinking is not too bad Bones, but just impractable to engineer, when really the same wing adjustment is easily achieved by simply pulling back on the stick. Most wing airfoils only operate in a small aoa area any way, generally in the region of say 2deg to 12-14 deg. The problem with pulling the stick back, is that is it is only temporary, for as you raise the aoa you create big drag, and pretty soon you've got to push the stick foward again.

 

So you need a clean wing for a fast cruise, and then lift producing devices such as large flaps, LE slats or VGs that come into play as you raise the aoa of the wing (pull back on the stick), to slow right down. This is very well demonstrated on say a Storch where the difference between a clean wing, and one with huge flaps out and the LE slats working, is very noticable both in speed and feel of the wing.

 

When using these hi-lift producing devices, you actually are changing both the camber, and aspect ratio of the wing, by altering the airfoil, chord, and often also effective wing area. So really it's two different wings in one, just by altering /deploying a few things.

 

One recreational aircraft that achieves the best of both worlds is the VG equipped Savanah. The relativly short clean wing achieves a pretty respectable cruise speed with the small fixed VGs creating only a minsicule amount of drag in cruise mode. However deploy some flap (full span incorporating the ailerons, ala Caribou) and the wing achieves pretty spectacular low-speed capabilities with the VGs now coming into play as the aoa increases, to keep airflow firmly attached to the top of the wing. It all works very well, and is safe, and predictable. A great easily achieved compromise, to achieve two totally different flight profiles...........................................................Maj...

 

 

Well yes I would agree that the gain is not huge, in terms of airspeed. However it is a free ride and when you look at the gain over say a years' flying, it is better than boot to the arxx......I first experienced reflex- flap on the Lightwing GA which has it standard with approx 5 deg up on the flaps. On a smooth-air morning flight I steadied the indicated AS at 60 kts with the reflex flap off. I then selected the reflex position and the AS went to 65-66 kts !!.....not really believing this myself I then de- selected it and the AS went back to 60Kts. It does work and on a plane like the GA LW can be a significant gain.................Maj...

The flaps of the Savannah are really below the wing to be more effective as flaps in the conventional sense. Just looking at the photos you posted, Maj, I think it may be difficult to alter the Savannah's flaps to be set up as negative flaps to get a free speed increase. Perhaps someone on the Forum has tried this on a Savannah, Storch or Zenith CH-701?

 

 

[facthunter]

You only need a big wing at low speed. Once you start going faster the angle of attack becomes quite low and not a good performance from a L/D point of view so your air miles/litre will not be good at high cruise speeds. A fowler flap A la Cessna with a bit of wash out is not a bad compromise. I always found the Cessna range of aircraft would do a good job at high weights and high density altitudes. (Well better than the other two) VG's help too. Nev

 

 

[Guest Crezzi]

Remember that old italian bloke Bernoulli???, his theory might just answer your question.

Wasn't he Swiss ?

 

Cheers

 

John

 

 

[AVOCET]

If you are talking rigger's angle of incidence ( which I assume you are) changing it will mainly affect the fuselage attitude in flight. The wing works the same.For a wing to lift at low speed , it needs lift devices like slats/slots for the Leading edge and efective trailing edge flaps,( slotted or fowler) or have "blown" wings. Other wise it will have a lot of area and a thick wing section, all of which mitigate against fast cuising. Nev

 

That's right , if you change the angle of incidence ( what your calling pitch ) will only change the position of the fuse in flight ,

 

The wing will always want to fly at about 3 deg . To the air flow .

 

In the situation you suggest ,as the aircraft left the ground (as you say 10deg pitch) it would pitch the the fuse down and Probly scare the "be -Jesus " out of you as the wing settles back down to 3deg ish

 

Cheers Mike

 

 

[facthunter]

Don't like Bernoulli as an explanation. More simply if you push a bit of air around it will push you back in the other direction. Any air that describes a curved path will have a lower pressure on the inside of the curve like on the top surface of a wing, otherwise it would go straight. Nev

 

 

[biggles5128]

Wasn't he Swiss ?Cheers

 

John

Yep I got that Italian bit wrong, he was actually Dutch born and died in Switzerland so well picked up John.

 

 

[Guest Maj Millard]

To maybe simplify the whole reflex thing further..(maybe) .the departing air coming off the trailing edge of the wing being forced downwards instead of straight back, becomes parasitic drag that the wing has to 'pull' along. The reflex actions straightens the air off the TE, therefore reducing the overall parasitic drag of the wing........it's really that simple as I see it.

 

Additionally because the air is coming off the TE cleaner, and more in line with wing itself, it's flow may even be slightly accelerated over the whole wing itself,therefore making the wing more 'efficient' requiring a possible power reduction, therefore saving fuel at cruise......

 

To possibly muddy the waters even further......could this effect also be related to 'getting on the step' that some wings do very well. By getting on the step you are aerodynamically holding the wing nose down and trailing edge up, also possibly straightening the departing airflow off the TE, and reducing the drag of the wing through the air ? ...........Maj...

 

 

[facthunter]

Eddy currents form in rivers and airflow patterns behind the separation point which is further forward when the wing is working hard, Ie High angle of attack. Air has mass and is viscous so these eddy flow patterns tend to persist due to inertia.

 

Maj, a lot of people don't believe in the getting it on the step theory calling it to an urban myth . It is more noticeable with large heavy aircraft cruising at close to their service ceiling. Accelerating to a higher airspeed blows some of the eddies away giving a cleaner airflow and you can cruise with a lower power setting. If you hit a parch of turbulent air they may re-establish and you slow up and stay slow unless you repeat the procedure. Nev

 

 

[Guest Maj Millard]

Well if many think it is an 'urban Mith' I must feel sorry for them as I, and many others routinely do it in many different types of aircraft. One may only assume either they have never attempted it, or don't have the 'feel' to successfully achieve it ?.....I do know from experience that in some aircraft types over certain routes with limited fuel capacity, if you don't get "on the step" you may well run out of noise due fuel exhaustion before reaching one's destination !!!!...........From past readings, the B-29 Superfortress was one type that benefited greatly in long legs over the Pacific by "getting on the step"........Maj...

 

 

[spacesailor]

It has been done before "Bones"

 

Very short takeoff & landinding with faily fast cruise! was called-----

 

Fairy RotorDyne,

 

The goverment at the time killed it off for their own shortcomeings, But it was a full size commuter plane

 

spacesailor.

 

 

[Mark11]

The Fairy RotorDyne is an amazing plane

 

Lots of good videos on YouTube

 

 

[spacesailor]

The Hummelbird has the uplifted ailerons to get a better cruise speed 140 knts max, but I'de like to make them into flaperons for a slower landing.

 

spacesailor