flap speeds?

[bagmaker]

Where can I learn about the optimum speed to fly in a particular flap setting?
I am flying a Mosquito, the handbook is not so easy for me to access.
Thanks in advance, Bagmaker.

[Bill Daniels]

I got this from someone on this group so take it for what it's worth. The
idea is that you want the lowest drag setting where the flap rides in the
wake of the wing. You can feel this with the flap lever.

With my Nimbus, I just unlock the flap lever and feel for a "neutral" point
where the airflow isn't pushing the flap up or down. Then, if I want to
slow down, I pull the flap lever into the next available positive detent.
If I want to speed up, I push it into the next negative detent. The result
seems very close to the POH suggestions.

Bill Daniels


"bagmaker" > wrote in message
...
>
> Where can I learn about the optimum speed to fly in a particular flap
> setting?
> I am flying a Mosquito, the handbook is not so easy for me to access.
> Thanks in advance, Bagmaker.
>
>
>
>
> --
> bagmaker

[SAM 303a]

I'll second what Bill. I too fly a Mosquito.
I go to -1 at 65kts.
I don't use -2.
In previous years I was using +.5 (someone put an additional notch in my
ship) and about 58kts for thermalling. This year I've slowed down to about
50kts and using +2. I'm getting a better rate of climb. Some advocate a
notch btwn +1 and +2.

"bagmaker" > wrote in message
...
>
> Where can I learn about the optimum speed to fly in a particular flap
> setting?
> I am flying a Mosquito, the handbook is not so easy for me to access.
> Thanks in advance, Bagmaker.
>
>
>
>
> --
> bagmaker

[rustynuts]

Can't believe that nobody knows about flap speeds?

[Doug Haluza]

The whole concept of flap speeds is really a misnomer, because the
optimum flap setting depends on angle of attack, so the flap speed
varies with weight. This is not as much of an issue if you always fly
solo and dry, but I fly a 2-place often with water, and my max gross is
almost double the empty weight.

The laminar flow airfoils used on most flapped gliders have a "drag
bucket" where the drag is much lower over a narrow range of AoA. By
adjusting the flap setting, you can move the drag bucket to a higher or
lower range. The notches in the available flap settings should be
designed to give some overlap in the drag buckets.

I have heard that the optimum flap setting is the one that produces no
force in the flap control, and I often let the flap handle float
between the 0 and -4 degree positions when in low speed cruise, but I
have no proof that this is correct. Does anyone have a reference
supporting this?

rustynuts wrote:
> Can't believe that nobody knows about flap speeds?

[Andreas Maurer[_1_]]

On 18 Nov 2006 04:16:48 -0800, "Doug Haluza" >
wrote:

>I have heard that the optimum flap setting is the one that produces no
>force in the flap control, and I often let the flap handle float
>between the 0 and -4 degree positions when in low speed cruise, but I
>have no proof that this is correct. Does anyone have a reference
>supporting this?

This was true for the older Wortmann (and alike) airfoils FX67-170
(Nimbus 2, LS-3 Pik-20, et cetera) , and FX62-K131 (ASW-17, ASW-20).

Current airfoils (ASW-27 et cetera) usually need a "push" to move them
into negative flap setting and generally lack the feedback that the
older aifoils provided.




Bye
Andreas

[Udo]

Doug Haluza wrote:
> The whole concept of flap speeds is really a misnomer, because the
> optimum flap setting depends on angle of attack, so the flap speed
> varies with weight. This is not as much of an issue if you always fly
> solo and dry, but I fly a 2-place often with water, and my max gross is
> almost double the empty weight.
>
> The laminar flow airfoils used on most flapped gliders have a "drag
> bucket" where the drag is much lower over a narrow range of AoA. By
> adjusting the flap setting, you can move the drag bucket to a higher or
> lower range. The notches in the available flap settings should be
> designed to give some overlap in the drag buckets.
>
> I have heard that the optimum flap setting is the one that produces no
> force in the flap control, and I often let the flap handle float
> between the 0 and -4 degree positions when in low speed cruise, but I
> have no proof that this is correct. Does anyone have a reference
> supporting this?
>

I use the flap setting as it is calculated for my airfoil and it works.
I would recommend using the factory recommended settings, as they have
also been tested. Some time later through experience in the field
it is found that an additional setting is required.
Here is what I think regarding setting the flaps by feel.
1. Friction within the system will distort the setting if it would be a
workable solution.
2. If one would want to fly at a given speed one would select that
speed first
but as soon as you move the flap the A of A changes hence the flap
setting changes again.
3 If you have two airfoil of different design but perform similarly for
a given speed range,
in one the C of P moves ahead of C of G and in the other it moves
behind.
What do we do now?
Generally most flap airfoils are back loaded, (C of P moves rear ward
with increased speed)
with flapless airfoil more so. Based on that I would say apply some
load to the flap.
But how does one know how much? Automated flap controls, as
describe in a technical article, are operated by g loads, having a
counterweight
applying a load to the flaps. I think those experiments were only
partly successful.
Udo

[bagmaker]

Thanks to all for the information and feedback.
Just thought I would boost this thread again.

After considerable playing, and with Bill Daniels best advice, I find that just flying at a chosen speed, -FEELING the lever feedback and picking the neutral point for that speed- seems to work best.

As stated, not much information is available (or easily available) for some older ships with flaps, and flapped craft are a little bit on the dark arts side to some around the bar. This should be corrected -the flap lever is a great thing to hold onto when your left hand is bored. According to articles by Mr Dick Johnson, thats perhaps all flaps are good for, depending on how you read it!

+2 (maximum) just seems to be too much, I get better results at higher speed when thermalling than full flap can produce, say 50 -52k. Some have advocated another notch between +1 & +2 on the mossie, pilot mass would have a bit to do with this as well!

So the bottom line is not to stress too much about flying a flapped ship, just let it flow best how it feels. Why the old farts at the bar cant just give you that I will never know.

Take-offs with full negative for aileron control is another issue!

Bagger

Happy Christmas too

[[email protected]]

assuming you flying a certified airplane:

FAR 21.333(c) specifies a 50 fps gust. This is what your Vno speed is
based on. Any faster than that, and penetrating a 50 fps gust will
exceed the G limits of the aircraft and ruin your day. Of course Vne
is faster than Vno so a lower gust velocity would still rip off the
wings or other flight critical component of you glider.

having a complete flight envelope should solve the problem, as the FAR
also points out a Vd (dive) gust line which would be the gust velocity
you could incur at max speed and still make it through.

if you are experimental, unless all the flight envelope info is somehow
available to you and you are sure yours was built right, all bets are
off.

bagmaker wrote:
> How does one figure how rough the air is?
> Consider that my final glide is happening at the end of the day, just
> one or two bubbles of lift remaining, and I am at Vne.
> Am I safe at this speed or should I only be going this fast if I am
> SURE that not one bubble remains, and no turbulant air will be flown
> into?
> Surely there is a recommendation on what constitutes "rough air" -or
> should I just limit my control input at this speed?
>
>
> Bagger
>
>
>
>
> --
> bagmaker

[J. Nieuwenhuize]

In fact for Jar (and I assume Far is less or more equal) at VNE the max
gust is only 7.5 m/s, and indeed double at VRA (25 vs 50 fps) Also pay
attention to the velocity at which VRA and VA are calculated, higher
wingloading means usually also a higher VA...
My rule of thumb: when there're no mountains and related phenomena VNE
is probally safe, except for thunderstorms. Of course that'd be
different with those 20 knots thermals in Texas ;-)


schreef:

> assuming you flying a certified airplane:
>
> FAR 21.333(c) specifies a 50 fps gust. This is what your Vno speed is
> based on. Any faster than that, and penetrating a 50 fps gust will
> exceed the G limits of the aircraft and ruin your day. Of course Vne
> is faster than Vno so a lower gust velocity would still rip off the
> wings or other flight critical component of you glider.
>
> having a complete flight envelope should solve the problem, as the FAR
> also points out a Vd (dive) gust line which would be the gust velocity
> you could incur at max speed and still make it through.
>
> if you are experimental, unless all the flight envelope info is somehow
> available to you and you are sure yours was built right, all bets are
> off.
>
> bagmaker wrote:
> > How does one figure how rough the air is?
> > Consider that my final glide is happening at the end of the day, just
> > one or two bubbles of lift remaining, and I am at Vne.
> > Am I safe at this speed or should I only be going this fast if I am
> > SURE that not one bubble remains, and no turbulant air will be flown
> > into?
> > Surely there is a recommendation on what constitutes "rough air" -or
> > should I just limit my control input at this speed?
> >
> >
> > Bagger
> >
> >
> >
> >
> > --
> > bagmaker