RE: flaps + elevator
 

That's an interesting remark ... How high ?

In addition, I guess 'reverse' is operational quickly too !

RE: flaps + elevator
 

I love flap discussions - -some really good info always pops up.
I have a question tho--
Flaps BIG advantage is in keeping the fuselage and its associated bits , at a LOWER angle, relative to angle of decent.
This means that the horizontal tailplane is ALSO decending at a lower AOA.
So the big question:
Doesn't the use of flaps really increase the relative efficiency of the horizontal tailplanes during decent?
Why is this never mentioned?
I recall an obscure NASA study , which showed the increased stability of a high AOA "mush",
thru actually keeping the entire horizontal tailplane AOA, aligned with the true path of flight.
Therefor--- in a flapped decent- the tailplane is at a lower AOA- than it would be if the plane were NON flapped and simply pitched to a high flare.
Too obscure???
If no one answers -I will hang up.

RE: flaps + elevator
 

around 60 to 70 % N1 on the glide full flaps is normal

reverse operations aren't accelerate. for two reasons
1) you are suposed to flare the airplane idle (this mean reduce the thrust to flight idle at the very end of the flare)
2) as soon your airplane nose gear will touch the ground the idle value will drop to ground idle (20% N1 instead of 40%n1 in flight)

unlock of the reverse is impossible when the airplane is in flight mode (for most of airliners)

in clean config, a airliner would easily track a 3 degrees glide slope in idle and the speed would be very hig
can check the numbers in the AOM I have here (747-dc10-737) but I think it's out of the subject

RE: flaps + elevator
 

Thanks for the information SalmonBug, let experimented people speak !

That reminds me of the 'Caravelle' (the first airliner in the world with both engines located at the rear of the fuselage) : it was a real glider :) ! Glide slope was lesssssssssss than 3 degrees...

RE: flaps + elevator
 

there was a story in my company about one of our chief pilot (this was 30 years ago) who took of from brussels in caravelle, climbed to somewhere like FL300 above the field, throtled back to idle , glided to paris and landed in "le bourget" without touching the throttle.

this story can be thrue, the only restriction i see is ATC consideration, but this was 30 years ago, so ATC was not yet what it is now

cl/cd max for a caravelle is somewhere around 30 if my souvenir are correct. flying at Dmin is very uncofortable, but a slight increase in speed in order to keep you on the right sight of the drag eas curve won't penalise you a lot in cl/cd ratio

by the way if cl/cd max was 30 like I guess, the minimum angle of descent =arcsin (1/30), mean 1.90 degrees
a normal approach glide path is 3 degrees


most of people think airliners are flying like bricks, this is not thrue, a 747 is a wayyyyyyyyyy more clean than a cessna 172 for exemple.

cl/cd max for a 747 is somewhere around 20 and must be somewhere around 7 for a cessna

RE: flaps + elevator
 

descent brain fade

RE: RE: flaps + elevator
 

my translating tool give me this result "les cerveaux de descente se fanent"
je me demande qui a le cerveau fané ici !

RE: flaps + elevator
 

When we engineers see "efficiency" we first think of nautical miles per pound of fuel. :)
This is seldom a concern with flaps down. Or with the military. under any condition.
The increased "efficiency" of a horizontal, flaps down might be considered a gift rather than something to be sought, unless there's something seriously wrong with the horizontal in the first place.
There;s no doubt a bunch of trade-offs in that area; adequate control for the worst flight condition, yet minimum interference at the best.
I see a lot of bottom views of the commercial jets going in and out of Burbank/Van Nuys, and there's two obvious but equally successfu contfigurations.. short tail moments, large horizontals and long tail moments, small horizontals...
And in the case of the MD-80s.. how does it fly at all? They took the wing too young from the mother, before it had time to grow up to be a real wing! :)

RE: flaps + elevator
 

natural reaction of a pilot will be to trim the horizontal stab, to regain the balance. i don't think that the change of aoa of the stab once the airplane is in trim will have any effect on the elevator behaviours (pilot inputs)

the only effect I know on elevator behaviours when flaps are down is the fact that the airflow is more turbulent on it and that this could result in loss of elevator control is some case and configuration, but it has nothing to see with the aoa

RE: Need help with flaps + elevator
 

I will try what you said, and see how this works. I guess the the thing to do if I stay with this radio,is to not use the flaps on take off , which I agree. I really do not need anyway. But they do look cool taking off. But they are a must for landing. I guess I should use 3/4 flap or full flaps. THey look real cool landing. If I do that I am going to have to put in quite a bit of elevator trim right? To do this I guess I need to fly at a good alitudtue and play with the flaps and elevator mix, this way I will not crash my plane.
Thanks for the help. I will let you how I turn out.

Pilot P51

RE: RE: flaps + elevator
 

The study was on a very high sink- way past what a pilot would see in flying any Gen Av or Commercial bird.
Simply a controlled deep sink - what the model flyers call a Harrier.
Again - the stab was pitched to match the angle the plane was taking in this "deep sink".
I would hate like hell to be in the thing.
On the models - typically there is lot of elevator control--like 45 degrees on an elevator which is over 50% of the horizontal tailplane--
This is sorta like what the study showed was a controllable setup.

RE: flaps + elevator
 

What did you mean [sm=confused.gif] ?

btw, what's that little dog ? a retriever ?

RE: RE: flaps + elevator
 

I spelled descent, decent.
Libby is a vey small version of a Lab-about 25 lbs. but the kids are adamant she is a Beagle/Cocker .

I will go for the Beagle - she bays - but somewhere there was a Lab in the mix.
She just learned to make air catches with the small flying disc .

RE: RE: flaps + elevator
 

Harrier....
It ain't all elevator. :)

RE: RE: flaps + elevator
 

We call that a sinking fun d

RE: RE: flaps + elevator
 

Dick, it's getting so ARFs are very very good airplanes! That one is electric powered and would be more than enough plane for me.. the glow versions I've seen fly equally well.
The prices are "attractive" in the amount of time not spent building, and the construction is pretty good.
That's Tony F's Funtana BTW..