STO, and fast cruise

[lark]

In addition to the 5 deg neg flap, the M7 also had an extra 8 deg of down flap. This was spring loaded to extend at around 50 knots taking full flap from 40 deg to 48 degrees. Don't know if any other GA aircraft had a similar system?

 

 

[David Isaac]

Yep pretty impressive performer. I remember years ago at Avalon where one took off across the strip and then virtually hovered in the brisk wind of the day.

 

 

[Yenn]

Avocet.

 

If your idea that the wing always goes to about 3 deg angle of incidence, can you explain what the elevator soes in flight.

 

 

[Guest nunans]

why not have the whole wing assembly to be pitch adjustable, so with the low cambered wing, with heaps of pitch to get off quick then slowly remove the pitch of the whole wing assembly, to get your fast cruise.

We already have this "adjustable pitch wing assembly"

 

We can adjust the wings pitch (or AOA) with the elevator.....

 

We even have an adjustable camber of some planes.. its called flaps....

 

 

[David Isaac]

and the slats ... don't forget the slats ... LOL

 

 

[eightyknots]

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...

It certainly works for some speedboats. Once you "get on the step" with them, the amount of power needed to keep moving forward reduces. However, if you happen to hit a big wave it can get you "off the step" and speed slows down until you get back on the step by increasing power for some time.

 

 

[AVOCET]

Avocet.If your idea that the wing always goes to about 3 deg angle of incidence, can you explain what the elevator soes in flight.

I was meaning that in strait & level flight the wings generally settle at about 3deg aoi .Its about getting the flight loads balanced (less drag). Some designers use two deg to try and get a better top speed , but I found that on the Avocet it made the tail fly a bit low in s/level.(more drag)

 

Obviously the elevator can change that ,

 

One of the checks is to see where the elevator sits in relationship to the vert./stab.in strait/level flight . If it sits high or low ,the the fix is to adjust the Angle of incidence of the wing , .

 

Then there's the compromise of settling on a position of the wing incidence to allow for different weights in the aircraft .

 

I found by having the load bed & engine close to the Cof G , that it made it easer to settle on a particular angle of inc.that gives the best overall performance .

 

Ref." principals of flight "by Kamode (think that's how you spell it)

 

Great book for beginners ,first year aeronautical engineering ,

 

It was one of the many aeronautical eng. (borrowed )books I studied for 3 years before I started the avocet program .

 

Ps What I was referring to in the post was that a fixed pitch of 10 deg in strait & level flight would give a large nose down attitude ,

 

Make a balsa model and try it out

 

Cheers Mike

 

 

[boingk]

It certainly works for some speedboats. Once you "get on the step" with them, the amount of power needed to keep moving forward reduces. However, if you happen to hit a big wave it can get you "off the step" and speed slows down until you get back on the step by increasing power for some time.

It baffles me that we are using nautical arguments, and I'm not referring to 80kt here but more the Rec Pilot community at large. The discrepancy and misuse of such terms is alarming.

 

Boats use a displacement method of buoyancy. Moving through the water when displacing a large volume of water is inefficient in general at speed, and is avoided by using a hull design that allows a craft to skip, or plane, over the water once at speed. Like boiling water, a relatively large amount of energy is expended reaching plane speed, and therafter a relatively small amount of energy is expended maintaining it.

 

Aircraft, on the other hand, move through the air in a relatively linear (energy expenditurely talking) way for a given attitude. Attitudes outside normal cruise are inefficient only because you will be increasing the angle of attack and approaching stall. Often it is more efficient to cruise at a slower speed then you may otherwise, or than the craft is capable of. Consult your POH for figures on cruise speed, fuel burn, and max range speed.

 

Please, everyone, stop using boats as an analogy. They are not aircraft and do not behave like them.

 

- boingk

 

 

[David Isaac]

A better analogy would be an 'aerofoil' (horizontal stabilizer) on a submarine and they don't get up on the step as a planing hull does.

 

 

[facthunter]

Aeroplanes have too much wing in cruise and not enough when they are going slow. Your aerofoil characteristics dictate the most efficient AoA which is a consideration with holding ( max time) or "ranging" ( max distance). Most planes cruise above the most efficient speed so have an AoA which is less than optimum. This fits with the concept of too much or too little wing quite well if you think about it.

 

When you "dirty" the wing up with Leading Edge Devices and slotted flaps etc you change the design of the basic aerofoil completely so more lift is available at lower speeds but the L/D ratio is worse. The lower approach speed is what you are after so you put up with the drag. Nev

 

 

[boingk]

Bingo.

 

This type of optioning for the wing is also what prevents us from cruising around in 200kt wonders - their stall speed would be very high by our current standards and not offer a lot of room for error. Look at the Formula One type aircraft (eg Cassutt Racer) in the US; they all use very small wing areas and thin aerofoils to give maximum speed, but tend to come in to land at frighteningly high speeds (90kt/100mph+) for such small aircraft.

 

We on the other hand have safety regs mandating a maximum stall speed, therefore we must have the wing area to make that possible. Although it makes our craft safer and easier to fly, it does hinder our top speed.

 

Cheers - boingk

 

 

[facthunter]

Placing flaps on the plane adds weight, complexity(and cost) and more drag even when retracted. There is an added risk of assymetric failure and often the stall speed reduction is only about 5 knots. Flapperons give more adverse aileron drag so are not all gain. Nev