TE flap deployment?

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pkelecy

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Unread post16 Sep 2013, 19:07

I know flaps are used during landing, and sometimes during take-off. Are there any other situations where the pilot would use these?

Also, when landing, how soon are flaps deployed? At the start of the landing approach?

Thanks for any feedback on this! :)
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Unread post16 Sep 2013, 19:19

in advanced aircraft like this they are automatically deployed when needed. Likely when the gear handle is dropped and the aircraft systems go into landing shedule (more lift needed at lower AoA measured from the nose)
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Unread post16 Sep 2013, 19:37

F-35C Opt AoA: VX-23 'Salty Dogs' F-35C Update - LCDR Ken “Stubby” Sterbenz
VX-23 Ship Suitability Department Head - Paddles Monthly - Sept 2010
"...Due to the fact that flap scheduling is completely automatic, the cockpit was designed without a flaps switch...."

http://www.hrana.org/documents/PaddlesM ... er2010.pdf (1.3Mb PDF)

All F-35s have the same cockpit with the exception in the B the red button initiates STOVL mode whilst in the A/C the same button puts the hook up/down.
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Unread post17 Sep 2013, 15:06

pkelecy wrote:I know flaps are used during landing, and sometimes during take-off. Are there any other situations where the pilot would use these?

Also, when landing, how soon are flaps deployed? At the start of the landing approach?

Thanks for any feedback on this! :)


The F-35 also uses it's flaps (trailing and leading edge) to airbrake. See the pics of the C model A-A refueling for a good example of this.
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lamoey

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Unread post17 Sep 2013, 15:58

I think the use of the leading edge flap is not for break purpose but to react to a specific AOA
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Unread post17 Sep 2013, 18:38

I think the term "flap" is a bit outdated for an aircraft like the F-35. The control surfaces along the leading and trailing edge of the wings are used for a number of purposes. In some cases the computer will deflect all of them down and they will act in the same manner as traditional flaps and slats. Normally this would be done to increase the coefficient of lift for the current airspeed. I would imagine the computer automatically and continuously changes the position of these control surfaces to achieve the most efficient wing configuration for the current flight conditions. In some cases it might intentionally choose to increase drag for deceleration however.
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Unread post17 Sep 2013, 20:20

OK then there is IDLC Integrated Direct Lift Control which in the case of the F-35C actuates the surfaces/flaps to achieve better response during a carrier approach.

http://www.youtube.com/watch?v=jlqRo3oB ... r_embedded (already indicated on the appropriate IDLC thread)
&
this is a repeat also:

Tailored to Trap Frank Colucci 01 Dec 2012
"F-35C control laws give Navy pilots Integrated Direct Lift Control for easier carrier landings, & they open the door for future landing aids....

...“A much better approach would be to control the coefficient of lift itself, by changing the camber of the wing.”

All three F-35 versions have trailing edge flaps to change camber. In addition, the longer-wing F35C has ailerons. The flaps normally droop 15 degrees in the landing configuration. However, active IDLC moves the flaps up and down from that reference point proportional to the rate of throttle movement. Canin said, “With IDLC, we change the symmetric deflection of the flaps and the ailerons in response to pitch and throttle commands by the pilot. The glideslope response is immediate, and doesn’t require a speed or alpha change. This is a tremendous advantage over a stiffwing airplane.”..."

http://www.aviationtoday.com/av/militar ... 77964.html
___________________

It is possible to search the forum for "IDLC" (without quotes) and this is one example:

http://www.f-16.net/index.php?name=PNph ... dlc#251972
___________________

& from: http://www.f-16.net/index.php?name=PNph ... dlc#201711

Naval joint strike fighter: A glimpse into the future of naval aviation Steve Weatherspoon c.Mid 2002
"...As noted earlier, the major deviation from commonality in the whole JSF family are design features for carrier suitability. The larger wing enables an approach speed of less than 140 knots with nearly 9,000 lbs of bringback. Just as importantly, the addition of ailerons, larger horizontal tails and rudders, and an innovative integrated direct lift control (IDLC) assure precise ball flying. The designers recognized early on that a relatively slick (due to stealth) configuration combined with a powerful, high rotational mass engine, could cause glide slope control problems. By integrating direct lift control (using drooped ailerons) with the throttle, the pilot is able to make near instantaneous glide slope corrections, using throttle only to precisely fly the ball. Full autothrottle and Mode I capabilities are also available. Outstanding results were demonstrated in 250 field carrier landing practice (FCLP) landings with contractor and Navy pilots in the X-35C Navy JSF test aircraft in the winter of 2001....""

http://findarticles.com/p/articles/mi_q ... _n9086493/

Note this article info is now 11 years out of date so do not take the figures as current (today). Tah.
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pkelecy

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Unread post20 Sep 2013, 17:34

Thanks for all the replies.

Didn't realize flaps were used during refueling, but did find the pictures showing that.

Any idea what the longest time duration flaps might be deployed for and in what operation? I thought that would landing, but now I'm not so sure.

I'm working on project trying to characterized how flaps/ailerons are used on modern fighter aircraft, and although I've found some information, the details tend to be slim. So I appreciate the help.

One other question. What is the correct term for these control surfaces on the F35A: flaps, ailerons, "flaperons"? I've seen all three used.
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Unread post20 Sep 2013, 21:49

The pilot has no control over the flaps in an F-35. They are deployed as required by the computer flight control system to achieve the pilot required flight conditions. There is no flap lever for the pilot to use. I hope that is clear. The flight control surfaces are used as the 'speedbrake' function:
"...Speed Brakes
...On the F-35, speed brake functionality is provided through the use of the rudders and leading- and trailing-edge flaps...."

http://www.codeonemagazine.com/article.html?item_id=28
________________________

Despite Setbacks, JSF Achieves Milestones By Chuck Oldham (Editor) - November 22, 2010

"...The bigger wing of the F-35C employs inboard flaps and outboard ailerons, beginning at the wing fold, for better control and slower approach speeds in the carrier landing environment, the other two variants using full span flaperons...."

http://www.defensemedianetwork.com/stor ... ilestones/

Only the F-35C has ailerons for better control during carrier approaches at low airspeeds. So it has 'flaps' and ailerons (but are the F-35C flaps also flaperons? The F-35A/B has no ailerons but flaperons. The IDLC moves the flaps during the F-35C approach but I'm not certain if the same applies to the F-35A/B flaperons during conventional landings - to achieve the result required by the F-35C approach precision. So you can see the computer flight controls do a lot of things that only concern the pilot if the desired result is not achieved. The pilot is not concerned how this is done ordinarily and the pilot does not control the flaps.

My guess is that the control surfaces, flaps/flaperons move any which way as required to achieve the pilot required aircraft response to control input. There is a great photo of an F-22 having all the control surfaces 'every which way but loose' during an airshow demonstration. I guess we will see this when the F-35 does low altitude airshows.

Here is a good explanation of how IDLC works on the F-35C for carrier approaches:

F-35C Integrated Direct Lift Control: How It Works Eric Tegler 09 Oct 2012
"IDLC will make carrier approaches easier...

...“What provides a huge benefit to the pilot is that [IDLC] moves the trailing edge flaps up or down to increase or decrease lift, which gives the airplane a very precise glide path control. It almost feels like a predictive control because it happens so quickly and you can get such effective changes in glide path. The trailing edge flaps are pretty large on the F-35C. For a carrier approach we nominally set them to 15 degrees trailing edge down, which is a half-flap configuration. So there’s room for the flaps to come down and to come up and either increase or decrease lift.”..."

http://www.defensemedianetwork.com/stor ... -it-works/

This test pilot says the flaps can be set at various angles on the F-35C. I'll imagine that the F-35C test aircraft have this control (by other means) whilst the production F-35Cs will not. What the test pilots are doing are testing the flight control laws that will automatically govern the aircraft and they are able to configure the aircraft to test different flight control settings - such as the flaps. Previously above the Test Squadron LSO said there is no flap switch in the cockpit (of the production aircraft).
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pkelecy

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Unread post22 Sep 2013, 20:07

Thanks spazsinbad! Sounds like the flight control on the F-35 is pretty sophisticated. Makes sense though. If a computer can do it better, why not let it.

I guess to get the information I was looking for I would need to have access to the flight control algorithms, (or know someone at LM). So I'll probably just have to take an (un)educated guess at it. :wink:

Thanks again. Appreciate the info. :)
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Unread post22 Sep 2013, 20:17

A lot of info about how STOVL flight control laws were developed via the VAAC Harrier on the web but ordinary F-35 flight control laws - not so much. Here is something mentioned a few times on this forum now but worth repeating perhaps....

Flight Control Law Development for the F-35 Joint Strike Fighter 05 October 2004 David W. Nixon, Lockheed-Martin Aeronautics

http://www.mathworks.com.au/aerospace-d ... eNixon.pdf (0.5Mb)
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