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Piper Arrow G-BVDH down on the Simplon Pass in Switzerland

Jacko wrote:

Best Angle of Climb – 78 mph IAS with flaps set @ Second Notch (24 degrees).
Just saying…

Best angle usually decrease with flaps as they push your polar power curve (ROC vs TAS) left and down as they shift max ROC down and shift VS left,
But tor take-off it is a different story as you have the combined 1/ initial ground roll & 2/ liftoff in ground effect & 3/ final climb
1/ needs clean flaps for better ground friction and drag trade-off (unless you have dragster)
2/ needs “take-off flaps” for better transition from ground friction and liftoff trade-off
3/ needs clean flaps but Vx is too close to VS0 at sea level

As you spend too much time in 2/, you would just go for “take-off flap” as it makes a better trade-off on ground friction, liftoff, climb angle without risking a stall, in theory, to get best angle on take-off, you should go with engine/surface/breaks settings that make you achieve VS with minimal distance in ground/liftoff and once in climb you fly according to Vx from polar without stalling…

Last Edited by Ibra at 19 Sep 11:09
ESSEX, United Kingdom

With flap extended both the lift coefficient increases and the limit load factor decreases so the minimum turn radius must decrease. If the optimum speed is not greater than the stall speed then any increase in drag that reduces the stall speed, so long as sufficient power available exists, must reduce the minimum turn radius.

If the minimum radius achieved at the higher stall speed is acceptable then extending flap, assuming sufficient power available exists, has the obvious advantage of increasing the margin above the stall speed and reducing speed instability.

I have never done a box canyon turn but is this theoretical argument consistent with standard practice?

London

Qalupalik wrote:

but is this theoretical argument consistent with standard practice?

For gliders, flying in tight thermals, yes you would go with some flaps for tight turns to maximize your overall RoC, how much? well it depends, you put flaps to fly slow with tight turns to maximize your RoC from thermals raising air at the core but not too much as it increase your sink rate in still air, while on final cruise you go for negative flaps as max lift is no longer your concern

The situation is different with power as wings will get loaded anytime turns happen straight and level, while flaps may help if you want a tight turns at small bank angles and slow speeds, I doubt this is the case as optimal bank angle ROB tend to be in 50 degrees region mainly from structural considerations:

Assuming you have enough power to stay level in the turn (e.g. a jet with afterburner) then your turn radius = V*V/tan(ROB) > VS*VS/[tan(ROB)*cos(ROB)], flaps reduces your base VS but they also reduce max ROB to stay with G or VFE limits, otherwise full flaps, fly near 90 degrees at max G and you will get minimum turn radius, in practice you don’t have power to stay level above 60 degrees and flaps are limited to +2G

Last Edited by Ibra at 19 Sep 15:15
ESSEX, United Kingdom

SkyDemon now also shows the GAFOR routes when you are flying, up until recently they would only show in planning mode.

Last Edited by HBadger at 22 Sep 16:01
Switzerland

Indeed; posted above. A little too late, perhaps.

Administrator
Shoreham EGKA, United Kingdom

Yes a bit too late unfortunately :(

Peter, just to be clear: my point was that now the GAFOR routes are shown in flight mode, which is another safety improving aspect in my opinion. Previous they would just vanish once you start flying. Now you are less likely to get confused whether you flew into the correct valley.
The post you linked to was about a different safety improvement: the confusion re recommended minimum crossing altitude is reduced by clearly showing it now.

Switzerland

Gigicret wrote:

GAFOR is not a navigation or planning system
GAFOR is a weather forecast on the road

I appreciate what a GAFOR really is, but having them shown (whatever you call them) on the Alpine passes (Skydemon) can be no bad thing. Well done the ‘movers & shakers’ who contributed to that.

Last Edited by WarleyAir at 30 Sep 00:28
Regret no current medical
Sandtoft EGCF, North England, United Kingdom

WarleyAir wrote:

I appreciate what a GAFOR really is, but having them shown (whatever you call them) on the Alpine passes (Skydemon) can be no bad thing. Well done the ‘movers & shakers’ who contributed to that.

It can be a very good thing.
But you should know that the altitude of the GAFOR is the altitude of the ground and not the altitude of flight.

It should also be known that GAFOR is not the only route possible and is not always the best option.
A pass on the GAFOR road may be closed, but a near pass can be open

LSGS, Switzerland

I really wish I (or somebody) had told this pilot to always climb to the altitude required for the entire pass before entering it (the simple safe option).

Administrator
Shoreham EGKA, United Kingdom

HBadger wrote:

SkyDemon now also shows the GAFOR routes when you are flying

It’s good to know SD do listen.

EGBW / KPRC, United Kingdom
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