Originally posted by mtnman
The claims "I" made about the flaps causing more lift were quotes from the manual. Who wrote those?
MtnMan
Hi,
more lift dont mean more lift over the full speed range, only more lift at slower speeds.
If you read in the link i posted before, you will find some hints to the influence of the bankangle to the list load and stall speed.
A little less thrust due to a higher drag already minimize the max possible bank angle while a sutained turn and this alone is a reason why planes with flaps dont turn as tight as someone would expect by comparing the stall speed(with vs without flaps).
F4UDOA,
we talk about a sustained turn here, i also believe that the F4U had a good initial turn, as long as there was speed to give up, otherwise i trust the other comparisons.
The FW190 also is a bad sustained turner, but while a highspeed turn it could turn with a Spitfire.
The AH F4U also turn very well without flaps as long as its fast.
I only question turn radius gain by using full flaps in a sustained turn, not only in the F4U, but this plane have BY FAR the highest advantage, while the P38 with the fowler flaps should have it(though, the P38 manouver flaps wasnt fowler flaps).
There was also other planes that could use the flaps in smal steps at higher speeds(109 for example), but they cant employ them above 190mph, what is a huge disadvantage.
For a very short runways it might be usefull to use full flaps for take off, while the liftgain full full flaps is rather smal, but a level flight is something absolut different than a banked flight, where the pilot need to fight side slip and yaw and where we need more power(more torque) to maintain altitude.
The planes are designed to manouver without flaps or with only a bit flaps at speeds good above stall speed. At slow speeds the alerons are not very effective anymore, while the plane like to yaw and swing, with other words, it get unstable, specialy if a huge torque effect work and the plane is banked.
http://www.canyonflying.com/canyonturns.htmlThis is also a very interesting article, from people who need to turn tight.
This is one of the more important parts:
"Another risk factor of steep turns is that bank angles beyond 30° rapidly increase the load factor and stall speed. For example, the load factor in a 30° bank is only 1.15 G with a 7.5% increase in stall speed. However, a 60° bank imparts a 2G load factor and a 41% increase in stall speed".
But our AH F4U-4 turn with less than 100mph, with full flaps and around 60 degree banking, absolutly alone, without the need to pull the elevator, only with a very smooth correction with the alerons.
Thats magic!
In a decelerated turn flaps will minimize the radius, but once at stall speed not many WWII flaps was able to reach that, simply cause the max lift at a given bank angle while a sustained turn dont increase much, but mainly shift to a slower speed. The little gain in max lift(if at all), at given bank angle while a sustained turn, get evened out by a much higher drag and much worse handling characteristics.
Only planes with endless power without torque (jets) would be able to take benefit by using ful flaps to decrease the turnradius that much in a sustained turn, but then most flaps couldnt stand the forces.
Would be interesting to see some CL diagrams of real WWII planes with split flaps and without flaps in comparison.
Interesting is, the AH F4U-4 turnrate remain almost the same with full flaps and without .
Greetings,
Knegel
