T/O & Lndg Gains

Operating an F-16 on the ground or in the air - from the engine start sequence, over replacing a wing, to aerial refueling procedures
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Patriot

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Unread post15 Dec 2017, 23:58

Thank you bouliult! I've almost got my head arround this topic finally. Would you please for the last time refer to situation below and share your thoughts... :thanks: I'd also like to hear the opinion of Gums or Johnwill if they're arround.


Patriot wrote: So, for example, situation: Flying in formation with slow mower at 200 knots (as in this pic below) in configuration likie this:
Handlingwise it would be better to stay in crusing gains and at considerably high AOA, or extend alt flaps and fly at lower AOA on t/o & l gains withh reduced maneuverbility?


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johnwill

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Unread post16 Dec 2017, 02:56

Patriot, it's been a long long time since I looked at this, but I believe the comment saberrider made about flaps not down above 370 kt and gear not down above 300 kt may be a little misleading. I could easily be wrong here, but I believe the alt flap is automatically scheduled between 300 kt (maybe?) and 370 kt. Meaning with alt flap down, below 300 kt the flaps will go full down, but as speed increases above 300, they will gradually retract until at 370, they are fully retracted. The full down flaps loads are ok at 370, but if the pilot chose to do a 9g turn at that time the wing torque loads would likely be excessive. Also the gear down limit speed is 300 kt, but it is not an automatic limit, it is a pilot observed limit. Limiting factor for gear down is of course the gear doors departing and probably causing serious damage to the airplane.
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saberrider

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Unread post16 Dec 2017, 08:04

Of course , Johnwill you're right about flaps up programing because retraction is not instantaneous and a/c gain some speed in @7 second's until they are up and gear limits .Thing is if you try to lowering flaps when you're flying above speeds limitations they don't go down due actuator's I believe or ignored electrical comand .
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bouliult

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Unread post19 Dec 2017, 20:53

saberrider wrote:Of course , Johnwill you're right about flaps up programing because retraction is not instantaneous and a/c gain some speed in @7 second's until they are up and gear limits .Thing is if you try to lowering flaps when you're flying above speeds limitations they don't go down due actuator's I believe or ignored electrical comand .


If the Alternate flap switch is positioned in ALT Flaps and the jet is going to fast for the extension of the Flaps they will simply not extend, however the jet will be in landing gains.

When lowering the speed and the ALT flaps switch is still in extend the Flaps will gradually come down. Max gear extend speed is 300kts. So when loweirnf the gear teh flaps will extend and gradually come down more during decelaration.
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bouliult

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Unread post19 Dec 2017, 21:01

Patriot wrote:Thank you bouliult! I've almost got my head arround this topic finally. Would you please for the last time refer to situation below and share your thoughts... :thanks: I'd also like to hear the opinion of Gums or Johnwill if they're arround.


Patriot wrote: So, for example, situation: Flying in formation with slow mower at 200 knots (as in this pic below) in configuration likie this:
Handlingwise it would be better to stay in crusing gains and at considerably high AOA, or extend alt flaps and fly at lower AOA on t/o & l gains withh reduced maneuverbility?


Flying with a slow mover below 200kts handling wise it will NOT be better to stay in cruise gains because the jet is not made to fly long times at those speeds. The pilot will be more 'in control'flying at very low speeds in landing gains. Be aware that flying at very low speeds in cruise gains will not leave the jet more agile compared to cruise gains suimply because the airflow is to little over the wings and flight controls. In landing gains the jet will be more forgiving. Typically when intercepting slow movers they will have the same problems as the Viper flying at low airspeeds.
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saberrider

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Unread post22 Dec 2017, 17:55

bouliult wrote:
saberrider wrote:Of course , Johnwill you're right about flaps up programing because retraction is not instantaneous and a/c gain some speed in @7 second's until they are up and gear limits .Thing is if you try to lowering flaps when you're flying above speeds limitations they don't go down due actuator's I believe or ignored electrical comand .


" If the Alternate flap switch is positioned in ALT Flaps and the jet is going to fast for the extension of the Flaps they will simply not extend, however the jet will be in landing gains".

When lowering the speed and the ALT flaps switch is still in extend the Flaps will gradually come down. Max gear extend speed is 300kts. So when loweirnf the gear teh flaps will extend and gradually come down more during decelaration.

Flaps they will simply not extend, however the jet will be in landing gains you tell me BUT in Take off Landing gains flaperons moves only SINGLE ONE UP if AILERONS COMMAND another one IS LOCK IN DOWN 20 DEGREES. SO IF YOU SEE MY DRIFT , NOW HOW IS TAKE OFF GAINS NOT ignored IF FLAPERONs ARE BLOWN UP BY excessive speed?
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bouliult

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Unread post23 Dec 2017, 23:00

saberrider wrote:
bouliult wrote:
saberrider wrote:Of course , Johnwill you're right about flaps up programing because retraction is not instantaneous and a/c gain some speed in @7 second's until they are up and gear limits .Thing is if you try to lowering flaps when you're flying above speeds limitations they don't go down due actuator's I believe or ignored electrical comand .


" If the Alternate flap switch is positioned in ALT Flaps and the jet is going to fast for the extension of the Flaps they will simply not extend, however the jet will be in landing gains".

When lowering the speed and the ALT flaps switch is still in extend the Flaps will gradually come down. Max gear extend speed is 300kts. So when loweirnf the gear teh flaps will extend and gradually come down more during decelaration.

Flaps they will simply not extend, however the jet will be in landing gains you tell me BUT in Take off Landing gains flaperons moves only SINGLE ONE UP if AILERONS COMMAND another one IS LOCK IN DOWN 20 DEGREES. SO IF YOU SEE MY DRIFT , NOW HOW IS TAKE OFF GAINS NOT ignored IF FLAPERONs ARE BLOWN UP BY excessive speed?


The flaps are not blown up by excessive speed they are commanded up by the Air Data Converter. The jet is still in landing gains even if the flaps are commanded more up because of airspeed.
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saberrider

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Unread post23 Dec 2017, 23:17

But in To/L .gains flaps(flaperons) only rice one at the time if the aileron's are apply (rolling)?That mean one is riced above the wing line and another one is not down at any degree. This is not possible.
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johnwill

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Unread post24 Dec 2017, 05:15

I think your understanding of the aileron command with TO/L gains is incorrect. In fact, aileron command sends equal and opposite command to the flaperons at all gains, normal or TO/L. Let's look at some numbers to help understand it better. At a speed of 200 kt, with flaps down they will be at 20 deg. If a right roll 5 degree aileron command is sent, left flaperon is commanded to 25 deg down, but 20 deg command limiter prevents it from moving. The right flaperon moves to 15 deg down.

Next increase speed to about 350 kt and the flaperons move to 5 deg down. Then apply the +/- 5 deg aileron command, so the left flaperon is commanded to 10 deg down and the right to 0 deg.

So you can say flaperon position with any gain is flap command +/- aileron command, limited to +/-20 deg.
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saberrider

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Unread post24 Dec 2017, 07:32

Thanks for clarification . I believed that if in To/L gains flaperons will stay only down position (20*)then with increase in speed rice up with no stoops between 20degrees down and 0 degree (once command up position will go to the 0 *).So if the speed is more than 300kts any position form 20 -0 is possible to have and applying aileron command is symmetrical up/down till20*max. down .That may be never20 up/20down aileron's in the slowly flight even though 23/21*is max. Cruise Gain because not need anything closely .
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saberrider

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Unread post04 Feb 2018, 12:36

Not to mention that flyng in landing gains the jet is much more limited in manoeuvrebility.[/quote]Half of roll rate , 17 max AOA.
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saberrider

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Unread post04 Oct 2018, 05:57

[/quote]
It goes with contrary with what Ive heard that using alt+flaps put LEFs in fixed position (either 15 or 25 degs supposingly).[/quote]

So if you have any AoA with the Alt Flap / or gear down setting then LEF's are deployed always more 15 degrees?
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