T/O & Lndg Gains

Unread postPosted: 10 Dec 2017, 14:46
by Patriot
Have a question.
How the T/O & landing gains (flcs mode set <400kts) affects the AOA, rool rate and yaw? Is the TO&L mode turned off as soon as the gear is up (in accordance with TEFs) or it stays on wehenever the jet is up to or below 400 knots?
Are CAT. III and Alt Flaps Mode independently put similar limitations to the airframe? I.e. AOA limit to 16-18 degs, roll rate cuted by half, yaw rate the same?
Any specific figures are welcomed!

ps. Does the alt flaps mode causes LEFs to be locked in place or not? Actually, does the alt flaps mode is operating under t/o&l gains or stand by ones?

Re: T/O & Lndg Gains

Unread postPosted: 11 Dec 2017, 07:03
by yooper65
This is what little I recall.. the Flight Control System is placed into Takeoff and Landing Gains either with the Landing Gear Control Handle being down, or Alt Flaps in Extend (and below 400 knots), or Air Refuel switch in Open (and below 400 knots).
I believe the Stores Config switch has no effect with FLCS while in Takeoff and Landing Gains. And the Alt Flaps switch has no effect on the LEFs with FLCS in Takeoff and Landing Gains.

Re: T/O & Lndg Gains

Unread postPosted: 11 Dec 2017, 10:10
by Patriot
Thank you for this clarification.

yooper65 wrote: And the Alt Flaps switch has no effect on the LEFs with FLCS in Takeoff and Landing Gains.

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

Btw, Ive read somewhere on this forum that if a (Viper) pilot switches alt flaps to extend, he's already in trouble..
Therefore my question. Can an Alt Flaps by any means be refered to as an emergency or an abnormal flight condition/procedure? (...as this feature was put in the jet originally to cope with an actual emergency/lndg gear mal)

Re: T/O & Lndg Gains

Unread postPosted: 11 Dec 2017, 15:26
by bouliult
Patriot wrote:Have a question.
How the T/O & landing gains (flcs mode set <400kts) affects the AOA, rool rate and yaw? Is the TO&L mode turned off as soon as the gear is up (in accordance with TEFs) or it stays on wehenever the jet is up to or below 400 knots?
Are CAT. III and Alt Flaps Mode independently put similar limitations to the airframe? I.e. AOA limit to 16-18 degs, roll rate cuted by half, yaw rate the same?
Any specific figures are welcomed!

ps. Does the alt flaps mode causes LEFs to be locked in place or not? Actually, does the alt flaps mode is operating under t/o&l gains or stand by ones?


The airspeed has nothing to do with being in Takeoff and landing gains. The jet is in these gains as said by putting the landing gear handle down, air refuel switch in OPEN, or the alt flaps switch in extend. Be aware that it only looks at the landing gear handle position. In landing gains the jet is not G/AOA rated as in cruise gains but is Pitch/AOA rated. This means that below 10 degrees AOA the jet is pitch rated (the jet wants to maintain pitch up/down attitude as inputed by the pilot opposed to cruise gains where it wants to maintain a constant G number untill app 12 degrees in CAT III and 20 degrees in CAT I) above 10 degrees AOA the AOA limiting is blended in. Also rollrate is limited.

The LEF’s are not affected by placing the alt flap switch in extend.

Alternate flaps may be used when you want to fly low airspeed with the gear up (slow mover intercept). But mostly it is used when there is something wrong. For example when for whatever reason you want to leave the gear handle in the up position. Or want to fly low airspeeds because of a canopy crack or a canopy that blew off.

The LEF’s will not schedule if there is a assimmetry between left and right LEF, when the the jet is operating in Standby gains or when they are placed in lock by the person in the cockpit.

Re: T/O & Lndg Gains

Unread postPosted: 11 Dec 2017, 23:41
by lamoey
Patriot wrote:Have a question.
How the T/O & landing gains (flcs mode set <400kts) affects the AOA, rool rate and yaw? Is the TO&L mode turned off as soon as the gear is up (in accordance with TEFs) or it stays on wehenever the jet is up to or below 400 knots?
Are CAT. III and Alt Flaps Mode independently put similar limitations to the airframe? I.e. AOA limit to 16-18 degs, roll rate cuted by half, yaw rate the same?
Any specific figures are welcomed!

ps. Does the alt flaps mode causes LEFs to be locked in place or not? Actually, does the alt flaps mode is operating under t/o&l gains or stand by ones?


It's been a few decades now, but I believe the <400kts, under 10,000ft (not sure of accurate alt.) and a certain sink rate gives the T/O warning light, to warn the pilot that the gear is not extended. I know a Norwegian viper managed to land with gear up, partly blamed on a low altitude, high speed circle, which prevented the sink rate to go over the limit, hence he got no warning about the impending belly landing.

Re: T/O & Lndg Gains

Unread postPosted: 12 Dec 2017, 12:31
by Patriot
Guys, bouliult exceptionally (it seem like you had some hrs on the thing) thank you for these explanations. On the other hand..

Gums (an ex-Viper driver I believe) back in 2006 somewhere else on this forum wrote something like this:

BTW, only time I ever used ALT FLAPS was trying to stay slow enuf to get tail numbers off a Cessna that was violatin restricted airspace. What a hoot.......

If you have to try something like ALT FLAPS, you're already in trouble, IMHO.


So my only question remains, what he meant by "trouble" ? :whistle:

Re: T/O & Lndg Gainst

Unread postPosted: 12 Dec 2017, 12:42
by bouliult
It's been a few decades now, but I believe the <400kts, under 10,000ft (not sure of accurate alt.) and a certain sink rate gives the T/O warning light, to warn the pilot that the gear is not extended. I know a Norwegian viper managed to land with gear up, partly blamed on a low altitude, high speed circle, which prevented the sink rate to go over the limit, hence he got no warning about the impending belly landing.[/quote]

The T/O warn light illuminates (just like the gear warning horn) when airspeed is below 190kts, alt less than 10000ft and vvi is more than 250ft/min negative and the trailing edge flaps are not extended and/or nosewheel not down and lockeed.

Re: T/O & Lndg Gains

Unread postPosted: 13 Dec 2017, 10:33
by yooper65
It appears during an Emergency Procedure that requires the Landing Gear Handle to be lowered but does not, the Pilot is to position the Alt Flaps Switch to Extend.

Re: T/O & Lndg Gains

Unread postPosted: 14 Dec 2017, 09:26
by saberrider
Patriot wrote:Thank you for this clarification.

yooper65 wrote: And the Alt Flaps switch has no effect on the LEFs with FLCS in Takeoff and Landing Gains.

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

Btw, Ive read somewhere on this forum that if a (Viper) pilot switches alt flaps to extend, he's already in trouble..
Therefore my question. Can an Alt Flaps by any means be refered to as an emergency or an abnormal flight condition/procedure? (...as this feature was put in the jet originally to cope with an actual emergency/lndg gear mal)
If F16 is in interception of an Cessna at @140knots AltFlap is used for lowering AoA and fly by next to the private plane.So No it is not emergency /abnormalities to drop the flaps .But fuel economy is important and why to fly with more drag if it is not required by mission or AR ?

Re: T/O & Lndg Gains

Unread postPosted: 14 Dec 2017, 12:39
by bouliult
saberrider wrote:
Patriot wrote:Thank you for this clarification.

yooper65 wrote: And the Alt Flaps switch has no effect on the LEFs with FLCS in Takeoff and Landing Gains.

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

Btw, Ive read somewhere on this forum that if a (Viper) pilot switches alt flaps to extend, he's already in trouble..
Therefore my question. Can an Alt Flaps by any means be refered to as an emergency or an abnormal flight condition/procedure? (...as this feature was put in the jet originally to cope with an actual emergency/lndg gear mal)
If F16 is in interception of an Cessna at @140knots AltFlap is used for lowering AoA and fly by next to the private plane.So No it is not emergency /abnormalities to drop the flaps .But fuel economy is important and why to fly with more drag if it is not required by mission or AR ?


Not to mention that flyng in landing gains the jet is much more limited in manoeuvrebility.

Re: T/O & Lndg Gains

Unread postPosted: 14 Dec 2017, 14:15
by Patriot
Got it.

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?

Image


lamoey wrote:I know a Norwegian viper managed to land with gear up, partly blamed on a low altitude, high speed circle, which prevented the sink rate to go over the limit, hence he got no warning about the impending belly landing.


wasn't that it?


Image

Re: T/O & Lndg Gains

Unread postPosted: 14 Dec 2017, 15:47
by saberrider
Thinking of this aspect : if the a/c is in To/L gains with flaps down it will have half off the response rates and may sunk a little when maneuver if you're heavyweight then you must not be aggressive in flight .But if refueling in the air this sluggishness will help you while make little corrections.

Re: T/O & Lndg Gains

Unread postPosted: 15 Dec 2017, 00:21
by Patriot
bouliult wrote:The airspeed has nothing to do with being in Takeoff and landing gains. The jet is in these gains as said by putting the landing gear handle down, air refuel switch in OPEN, or the alt flaps switch in extend.


You're saying that if I'd fly at say Mach 1.5 and put an air refuel switch to open the jet would go into takeof & landing gains?

Re: T/O & Lndg Gains

Unread postPosted: 15 Dec 2017, 21:23
by saberrider
Patriot wrote:
bouliult wrote:The airspeed has nothing to do with being in Takeoff and landing gains. The jet is in these gains as said by putting the landing gear handle down, air refuel switch in OPEN, or the alt flaps switch in extend.


You're saying that if I'd fly at say Mach 1.5 and put an air refuel switch to open the jet would go into takeof & landing gains?
Limitations are present and flaps cannot stay down over speed limit of 370knots and gear over 300

Re: T/O & Lndg Gains

Unread postPosted: 15 Dec 2017, 22:32
by bouliult
Patriot wrote:
bouliult wrote:The airspeed has nothing to do with being in Takeoff and landing gains. The jet is in these gains as said by putting the landing gear handle down, air refuel switch in OPEN, or the alt flaps switch in extend.


You're saying that if I'd fly at say Mach 1.5 and put an air refuel switch to open the jet would go into takeof & landing gains?


Affirm. That is it. Off course the speed limit is 400kts 0.85 mach fit selecting Air refuel open.

Re: T/O & Lndg Gains

Unread postPosted: 15 Dec 2017, 23:58
by Patriot
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?


Image

Re: T/O & Lndg Gains

Unread postPosted: 16 Dec 2017, 02:56
by johnwill
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.

Re: T/O & Lndg Gains

Unread postPosted: 16 Dec 2017, 08:04
by saberrider
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 .

Re: T/O & Lndg Gains

Unread postPosted: 19 Dec 2017, 20:53
by bouliult
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.

Re: T/O & Lndg Gains

Unread postPosted: 19 Dec 2017, 21:01
by bouliult
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.

Re: T/O & Lndg Gains

Unread postPosted: 22 Dec 2017, 17:55
by saberrider
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?

Re: T/O & Lndg Gains

Unread postPosted: 23 Dec 2017, 23:00
by bouliult
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.

Re: T/O & Lndg Gains

Unread postPosted: 23 Dec 2017, 23:17
by saberrider
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.

Re: T/O & Lndg Gains

Unread postPosted: 24 Dec 2017, 05:15
by johnwill
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.

Re: T/O & Lndg Gains

Unread postPosted: 24 Dec 2017, 07:32
by saberrider
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 .

Re: T/O & Lndg Gains

Unread postPosted: 04 Feb 2018, 12:36
by saberrider
Not to mention that flyng in landing gains the jet is much more limited in manoeuvrebility.[/quote]Half of roll rate , 17 max AOA.

Re: T/O & Lndg Gains

Unread postPosted: 04 Oct 2018, 05:57
by saberrider
[/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?