negative flaps--what speeds?

The manual for my 303 Mosquito is silent as to when the use of negative
flaps becomes beneficial during cruise. Any pointers as to what speeds are
associated with -1 and -2 flap positions? Any data on the LD benefits of
negative flaps at higher speeds?

I read Dick Johnson's flight eval (Aug '79) and my take away is that it
makes sense to go to -1 (4.6 degrees) at around 80 kts and that there's
little difference between -1 and -2. I also understood that article to say
that the speed of best LD could be increased by 5 kts by using -1. Is my
understanding on these two points correct? Dick says the weather was poor
and there was a lot of scatter in the data--does anyone have experience that
agrees/disagrees with Johnson's report?

Any help appreciated--specific to the 303 or regarding flap use during
cruise in general. Hey, I'm transitioning from a PW5 to a 15M and it's got
a lot of new thingies to get used to--retractable wheel, flaps, water,
LEGS!!! ;-)

Brent

I would recommend a flap setting for the FX 67 170 of
-4 deg. starting at ~50 kt and changing over to - 8 at 70-75 Kt.
The Airfoil analysis agrees with the R.Johnson statement,
the L/D is better with -4 Flap
Udo

"303pilot" brentUNDERSCOREsullivanATbmcDOTcom wrote in message ...
The manual for my 303 Mosquito is silent as to when the use of negative
flaps becomes beneficial during cruise. Any pointers as to what speeds are
associated with -1 and -2 flap positions? Any data on the LD benefits of
negative flaps at higher speeds?

I read Dick Johnson's flight eval (Aug '79) and my take away is that it
makes sense to go to -1 (4.6 degrees) at around 80 kts and that there's
little difference between -1 and -2. I also understood that article to say
that the speed of best LD could be increased by 5 kts by using -1. Is my
understanding on these two points correct? Dick says the weather was poor
and there was a lot of scatter in the data--does anyone have experience that
agrees/disagrees with Johnson's report?

Any help appreciated--specific to the 303 or regarding flap use during
cruise in general. Hey, I'm transitioning from a PW5 to a 15M and it's got
a lot of new thingies to get used to--retractable wheel, flaps, water,
LEGS!!! ;-)

Brent

At 18:36 24 July 2003, 303pilot wrote:
The manual for my 303 Mosquito is silent as to when
the use of negative
Hi Brent

I am a Mosquito owner.
I have found that normal thermalling is best done at
around the 45-50kt range with +1 flap. I have flown
in weak wave where at around 50knots the glider was
sinking and putting the flaps up to 0 enabled the glider
to climb. The drag is obviously less in the higher
(up) flap setting

When cruising I put the flaps in whatever position
feels comfortable with little reference to the ASI,
other than to monitor the chosen cruise speed. The
way to do this is quite simple, once you start to increase
speed move the flap lever into the free position and
without letting go, let it float. You will find that
it adopts a set position which can be felt, for a given
speed, then you can drop it into the closest notch.
After a while this becomes automatic.

Two other simple techniques are

1. When leaving a thermal put the flaps right up
before you accelerate, on some gliders like the ASW20
putting the flaps up causes a quite marked speed increase,
the Mosquito is not quite so marked and need a little
help from the stick. One you have reached your chosen
cruise speed you can then reset the flaps as required.

2. Only put the flaps down when you have slowed after
your pull up into the next thermal.

This means you are accelerating and decelerating with
minimum drag and do not have to worry about the speed
settings as you speed up and slow down.

Landing the Mosquito is a whole new ball game!! The
was a thread running a few months ago on this subject.

Hope this helps

Dave Martin

Someone (I do not remember the name) wrote in last years Soaring magazine about quite contrary
approach (not related to specific glider). The idea was that one has to put flaps down WHILE slowing
down, not after. And the reasoning was that flap position is not that much depending on the speed of
the glider, but on angle of attack. So if one attacks thermals aggressively making serious pull-ups,
the increased AOA means one has to advance in flap settings beforehand the lowering speeds. Same
applies to leaving the thermal cause then the AOA decreases. It was told to be making huge
differences.


Regards,
Kaido, who doesn't fly flapped gliders currently.



2. Only put the flaps down when you have slowed after
your pull up into the next thermal.

This means you are accelerating and decelerating with
minimum drag and do not have to worry about the speed
settings as you speed up and slow down.

Sorry, It was in 2001, but I still don't remember the specific article and the writer.


"iPilot" wrote in message ...
Someone (I do not remember the name) wrote in last years Soaring magazine about quite contrary
approach (not related to specific glider). The idea was that one has to put flaps down WHILE
slowing
down, not after. And the reasoning was that flap position is not that much depending on the speed
of
the glider, but on angle of attack. So if one attacks thermals aggressively making serious
pull-ups,
the increased AOA means one has to advance in flap settings beforehand the lowering speeds. Same
applies to leaving the thermal cause then the AOA decreases. It was told to be making huge
differences.


Regards,
Kaido, who doesn't fly flapped gliders currently.



2. Only put the flaps down when you have slowed after
your pull up into the next thermal.

This means you are accelerating and decelerating with
minimum drag and do not have to worry about the speed
settings as you speed up and slow down.

The method Dave described is what I normally do in my LS-3a. Yesterday
I was trying some different settings and noticed that at 100 knots,
the flaps could be moved between 0 and -7 with no issues. At 120 knots
the flaps wanted to stay at about -3 and when I moved them to -7,
which required some pressure, it created a humming noise. Seems that
-7 should be better at higher speeds but the noise and pressure on the
flap handle tells me otherwise.

Also, the LS-3a Flight Manual has the following instructions:

Up to 103 knots - Flaps should be between 0 and -7, depending on
desired speed. Once the aircraft is trimmed for thermaling, no
additional trim adjustment is required for high speed flight. Any
stick forces can be removed by adjusting the flap position. This
results in the correct flap position for all speeds.

103 ~ 146 knots - Flap position -7. Stick forces should be reduced to
zero through trim adjustment.

All the best,
Steve

Dave Martin wrote in message ...

snip

When cruising I put the flaps in whatever position
feels comfortable with little reference to the ASI,
other than to monitor the chosen cruise speed. The
way to do this is quite simple, once you start to increase
speed move the flap lever into the free position and
without letting go, let it float. You will find that
it adopts a set position which can be felt, for a given
speed, then you can drop it into the closest notch.
After a while this becomes automatic.

snip

Dave Martin

Kaido

Read, 'Advance Cross Country Soaring' by John Delafield.
Pages 81 Flaps

John gives a detailed account of the use of flaps,
which agrees with what I said, or more to the point,
there were few articles written on the correct use
of flaps in 1983 and the information from John helped
me learn how to use the flaps.

In summary he says, 'Flaps should be not be regarded
as anything other than an auxilary control to enable
the pilot to operate the wing efficiently throughout
the speed range. The are straight forward in use and
will become instinctive after only a few hours' practice.'

The method described is simple and reduces the movements
to a minimum and saves the pilot worrying what the
next setting should be.

Flaps UP to slow down. Flaps UP to accelerate, then
once the
required speed has been achieved set them to support
flight at that speed.

The only word of caution is that in large pull ups
and push overs with reduced G at the top and increased
stall speed because of the negative flap setting the
pilot may be in serious danger of spinning.



At 08:24 25 July 2003, Ipilot wrote:
Someone (I do not remember the name) wrote in last
years Soaring magazine about quite contrary
approach (not related to specific glider). The idea
was that one has to put flaps down WHILE slowing
down, not after. And the reasoning was that flap position
is not that much depending on the speed of
the glider, but on angle of attack. So if one attacks
thermals aggressively making serious pull-ups,
the increased AOA means one has to advance in flap
settings beforehand the lowering speeds. Same
applies to leaving the thermal cause then the AOA decreases.
It was told to be making huge
differences.


Regards,
Kaido, who doesn't fly flapped gliders currently.



2. Only put the flaps down when you have slowed after
your pull up into the next thermal.

This means you are accelerating and decelerating with
minimum drag and do not have to worry about the speed
settings as you speed up and slow down.

Whilst all this theory makes sense ---- to some, my
glider manual only has the single polar curve which
itself is a guestimate from a comparison flight with
a 16 metre Standard Cirrus B

I like to keep my flying simple, John Delafields method
works it is simple and in flight uncomplicated. I
suspect the savings on drag produced by speeding up
or slowing down with flaps in a negative, up, position
is relatively small.

Whereas putting flaps down at speed to slow down appears
very inefficient.

Still if you are happy with this loss of energy then
fine.

Dave Martin

Andreas,

Without wanting to prolong the argument
There appear to be two ways of achieving the same objective,
pilots should just chose the one they are happy with.
I trust the John Delafield theory and find it works,
others prefer yours and Berts

Dave
14:06 26 July 2003, Andreas Maurer wrote:
On Fri, 25 Jul 2003 14:31:35 +0200, 'Bert Willing'
wrote:

Flaps are just a pitch control which is more direct
than the stick. I do
accelerate by pushing the flaps to negativ, and I deccelerate
by pulling
them to positive settings. Works very nicely (but still
using the stick :-)
I don't see why I should use negativ flaps to pull
up.

Yup. Always keep the AoA constant by using the flaps.
I think the procedure that is described in the ASW-20's
manual
describes the physics very well.

Bye
Andreas

I have seen a mirror with a level type of device attached to the panel to help
set flap positions, Sean Franke's Ventus has this. I I do not know how it
works but was hoping someone has used sucha device and could comment.

Craig