Time in seconds to retract flaps after takeoff.

Always wondered why the F-16 has a tailhook, or how big a bigmouth F-16's mouth really is ? Find it out here !
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saberrider

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Unread post21 Oct 2016, 07:25

During takeoff the landing gear retract time is set at a known value (second's) but flaps retraction after takeoff it looks bit longer.Is this delay the same every time or not ? Why?
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basher54321

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Unread post21 Oct 2016, 13:22

It would make sense to me to keep the Flaperons down until a certain speed is reached (for the current stores configuration) so there is enough lift for safe flight when they are fully retracted.
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saberrider

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Unread post21 Oct 2016, 19:26

basher54321 wrote:It would make sense to me to keep the Flaperons down until a certain speed is reached (for the current stores configuration) so there is enough lift for safe flight when they are fully retracted.

And how you'd know there is enough lift for current stores (charts with speeds) or pitch increased by itself and then you retract landing gear together with flaps ?
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Unread post21 Oct 2016, 21:52

saberrider wrote:And how you'd know there is enough lift for current stores (charts with speeds) or pitch increased by itself and then you retract landing gear together with flaps ?


The pilot must calculate/know the minimum speed he can take off at - and that speed will be different depending on weight and the stores.
Once that speed is achieved the pilot then pulls back on the stick and then once airborne needs to raise the Landing Gear before going over the gears speed limit.
Once the Landing Gear handle is raised under normal operation the Flaperons are supposed to retract but are still under the control of the flight control system.
As I understand it at slower speeds (with the gear fully raised) the Flaperons come down to provide lift regardless and the angle they drop is dependent on the current speed (the FLCS might consider weight as well but I don't know). So what you are seeing I would guess is due to being under a certain speed (as opposed to being part of their Aileron function).
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saberrider

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Unread post21 Oct 2016, 23:46

basher54321 wrote:As I understand it at slower speeds (with the gear fully raised) the Flaperons come down to provide lift regardless and the angle they drop is dependent on the current speed (the FLCS might consider weight as well but I don't know).

It is for the first time when someone talk about flaperons in F16 come down at slow speed by FLCS and not by selecting Alt Flap(with the gear fully raised).NEVER .
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basher54321

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Unread post22 Oct 2016, 01:39

saberrider wrote:It is for the first time when someone talk about flaperons in F16 come down at slow speed by FLCS and not by selecting Alt Flap(with the gear fully raised).NEVER .


Sorry I might be wrong there was thinking they come down with the LEFs. :oops:

Where are the sample videos? - that I should have asked for first.
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35_aoa

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Unread post22 Oct 2016, 04:26

Could be different in higher block jets, but in mine (normally without stores), 180 knots is about the minimum airspeed you want to bring the gear (and flaps) up. Much lower than that, and you are risking settling back onto the runway.
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35_aoa

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Unread post22 Oct 2016, 04:27

basher54321 wrote:
saberrider wrote:It is for the first time when someone talk about flaperons in F16 come down at slow speed by FLCS and not by selecting Alt Flap(with the gear fully raised).NEVER .


Sorry I might be wrong there was thinking they come down with the LEFs. :oops:

Where are the sample videos? - that I should have asked for first.


Not sure if this is what is being asked, but you can force the FLCS into takeoff/landing gains with the gear up by selecting ALT Flaps. Really only a player in an emergency.
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saberrider

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Unread post22 Oct 2016, 05:03

35_aoa wrote:
basher54321 wrote:
saberrider wrote:It is for the first time when someone talk about flaperons in F16 come down at slow speed by FLCS and not by selecting Alt Flap(with the gear fully raised).NEVER .


Sorry I might be wrong there was thinking they come down with the LEFs. :oops:

Where are the sample videos? - that I should have asked for first.


Not sure if this is what is being asked, but you can force the FLCS into takeoff/landing gains with the gear up by selecting ALT Flaps. Really only a player in an emergency.

I wanted to know if F 16 flaps (TEF)have a fixed rate to retract or it will be variable with the speeds.The landing gear is retract at pilot desire but no at the same speed every time ,so TEF must coupe with this speeds.Landing gear actuators have retract/deploy time the same every time.That why I put second's as reference.But flaperons to deploy/retract time will be or not same every time due to difference in speeds ?And LEFs are dropped at only 15 degrees because takeoff/landing configuration or because of AOA during landings?
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Unread post22 Oct 2016, 12:11

35_aoa wrote:
Not sure if this is what is being asked, but you can force the FLCS into takeoff/landing gains with the gear up by selecting ALT Flaps. Really only a player in an emergency.


Hi 35 - I don't suppose you ever cared about what was happening here but if Alt flaps was left in extend at takeoff (for whatever reason) that should cause a delay in full flap retraction based on speed should it not?
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saberrider

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Unread post22 Oct 2016, 12:50

basher54321 wrote:
35_aoa wrote:
Not sure if this is what is being asked, but you can force the FLCS into takeoff/landing gains with the gear up by selecting ALT Flaps. Really only a player in an emergency.


Hi 35 - I don't suppose you ever cared about what was happening here but if Alt flaps was left in extend at takeoff (for whatever reason) that should cause a delay in full flap retraction based on speed should it not?

Somewhere in this forum is specified a max .speed of 370 Knots to fully blow back flapeons and landing gear retraction is 300knots.Why do you put Alt flaps switch in extend position at takeoff??FLCS already have them deployed on taxi.
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MVSGas

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Unread post22 Oct 2016, 15:49

I do not think there is a delay for the falperon retraction. I thought, IIRC, that they came up when the gear hit the uplock switch, at about the same rate of movement as the gear doors, so by the time doors are close the flaperons where up.
From the -1
As aircraft lifts off, LEF’s extend downward. Retract LG
when safely airborne. Insure LG is up and locked before
exceeding 300 knots. TEF’s retract when the LG handle is
raised.
WARNING
Since LG and TEF retraction occurs simultaneously, LG retraction should not be rushed
after takeoff. The reduction in lift may cause
the aircraft to descend and contact the runway.
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MVSGas

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Unread post22 Oct 2016, 16:03

basher54321 wrote:It would make sense to me to keep the Flaperons down until a certain speed is reached (for the current stores configuration) so there is enough lift for safe flight when they are fully retracted.

AFAIK, the only speed that matters for the flaperons is high speed.
At all airspeeds below 240 knots, the TEF position is 20 degrees
down. Above 240 knots, the TEF’s reduce deflection as a
function of airspeed until nearly/fully retracted at 370 knots.
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basher54321

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Unread post22 Oct 2016, 17:16

MVSGas wrote:
AFAIK, the only speed that matters for the flaperons is high speed.

At all airspeeds below 240 knots, the TEF position is 20 degrees
down. Above 240 knots, the TEF’s reduce deflection as a
function of airspeed
until nearly/fully retracted at 370 knots.


And the above should happen when either the LG handle is down or the Alt Flaps switch is set to Extend. And I am reading that between 240kts and 370kts the Flaperons are set down at an angle (under 20 degrees) depending on airspeed.
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saberrider

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Unread post22 Oct 2016, 17:38

basher54321 wrote:
MVSGas wrote:
AFAIK, the only speed that matters for the flaperons is high speed.

At all airspeeds below 240 knots, the TEF position is 20 degrees
down. Above 240 knots, the TEF’s reduce deflection as a
function of airspeed
until nearly/fully retracted at 370 knots.


And the above should happen when either the LG handle is down or the Alt Flaps switch is set to Extend. And I am reading that between 240kts and 370kts the Flaperons are set down at an angle (under 20 degrees) depending on airspeed.

Carefree handling at low speed and FLCS drop off the flaps by itself no pilot input. Like a F18 Hornet?If the speed increasing FLCS retract flaps a bit but not totally, you say. Thanks for reply.Learned some new things about Viper today.At minimum speed -110 Knots and 25degree's flaps are extended to fly level .But then you are in To/L gains and it is impossible to reach 25 degrees AOA. Something is not right here !!!
Last edited by saberrider on 22 Oct 2016, 19:28, edited 2 times in total.
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