F-35 Approach AOA

Discuss the F-35 Lightning II
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neutrino

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Unread post12 Jan 2010, 11:25

Hi guys, can you give me an estimate about what you think will be the landing approach optimum AOA for the F-35? It seems that it is high - similar to the F-16 (11 degr) - rather than low compared to the F/A-18 (8.1 degr)... The speed of course will depend on weight and CG position. I also wonder if it will be using the virtual speed brake even prior to touch down, or after touchdown?
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What is the approach AOA...?
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What is the approach AOA...?
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spazsinbad

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Unread post12 Jan 2010, 12:29

G'day neutrino, I'll keep looking for Optimum AoA airspeed etc but be aware: "While it shares its fundamental design with the F-35A (conventional takeoff and landing) and F-35B (short takeoff/vertical landing), the F-35C is specialized for the catapult launches and arrested recoveries of large aircraft carriers. It features 30 percent more wing area than the other two variants, larger tails and control surfaces, and wingtip ailerons – all contributing to the precise slow-speed handling characteristics required for carrier approaches. The F-35C’s internal structure is strengthened to withstand the punishment of repeated catapult launches and arrested recoveries on the carrier deck."

Which JSF variant AoA do you seek? If JSF-C this PDF is helpful in a general sense: http://handle.dtic.mil/100.2/ADA399988 [1Mb] "The Influence of Ship Configuration on the Design of the Joint Strike Fighter"
Last edited by spazsinbad on 12 Jan 2010, 22:23, edited 1 time in total.
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dino1974

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Unread post12 Jan 2010, 13:37

@neutrino

I think I know why you are asking the AoA question...
Thanks for your help with the FSX model. BTW I hope I will be able to pack the Beta 1 tonight.

@ Spazsinbad

Interesting read - I'd really want to make a -B and -C models for Flight Simulator and hope I can find the time one day or another...
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dino1974

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Unread post12 Jan 2010, 13:56

My apologies to all the other readers of this forum if my previous comment seems a bit cryptic.
I'm developing a model of the F-35 for Flight Simulator X - the test version is almost complete and the package should be ready in a month or so (hopefully).

The package, at present, will depict the CTOL versions of the Lighting II and will include a 3D virtual cockpit. I'm trying to make it reasonably realistic, but there will be several compromises due to the limits of FSX, of my knowledge and my time.

BTW - during the development of this project, this forum has been an invaluable source of information.
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spazsinbad

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Unread post12 Jan 2010, 14:07

G'day Dino, finding exact information is not so easy but... (info below may be 'out of date'):

The Joint Strike Fighter: A plane for all reasons March 7, 2002 by Stephen J. Mraz

http://machinedesign.com/article/the-jo ... asons-0307

"FLY NAVY [USAF JSF-A approach approx. 160KIAS]
Carrier operations account for most of the differences between the Navy and other JSF variants. Carrier landings, for example, are so severe, they're often referred to as "controlled crashes." The JSF, in a low speed approach to a carrier landing, will descend at about 11 fps, and will withstand sink rates up to almost 18 fps. By comparison, the typical sink rate for an Air Force JSF will be about two ft/sec.

To help handle better at low speeds, the aircraft will have larger wing and tail-control surfaces. The increased wingspan also boosts the strike-fighter's range and weapon or fuel load. Even without external fuel tanks, the JSF has almost twice the range of the F/A-18C. Larger leading-edge flaps and wingtips provide the extra wing area, while the wingtips fold so the aircraft takes up less space on the carrier's crowded flight and hangar decks. The Navy's JSF will also have two extra control surfaces — ailerons outboard of the flaperons on the wings — for additional lowspeed control and flying precise glide slopes. The Navy JSF currently flies landing approaches at about 130 to 135 knots, about 25 knots slower than the Air Force version."
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LONG STORY HERE:

http://www.codeonemagazine.com/archives ... index.html
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dino1974

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Unread post12 Jan 2010, 15:30

@ Spazsinbad

Thanks, another interesting read - although it seems to refer to the X-35A...
Now, I beginning to think it would be better, for me, to stop reading about the F-35 as the more I read and the more I'd like to add features and details...which would be a good thing if I had the time to implement them...
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Unread post12 Jan 2010, 20:54

Just for the record (whilst these Optimum AoA & Approach Airspeed figures seem to be difficult to find....) a recent Key Performance Parameter [KPP] figure for USN 'Maximum Approach Airspeed' is 145 KIAS.
RAN FAA A4G: http://tinyurl.com/ctfwb3t http://tinyurl.com/ccmlenr http://www.youtube.com/user/bengello/videos
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neutrino

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Unread post12 Jan 2010, 21:47

Hi Spaz, thanks for the info and references - that was exactly what I was looking for ! I doubt that we will find a reliable data for optimum AOA, but at least the difference in approach speed between CV and CTOL variants (25 kts) is a very useful info. Also it seems that the CV may have a lower AOA to improve visibility.

The 145 kts maximum approach speed you quote is due to arresting gear limitations.

As to Dino's F-35 project - he has done an absolutely outstanding job of modeling the AA-1 prototype. Check out this picture from his blog which is my favorite...
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spazsinbad

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Unread post12 Jan 2010, 22:14

neutrino, no probs. IMHO the 'lower AoA' as you state does not make sense (except perhaps 'lowering the nose to have a better Field of View FOV during a carrier approach). Perhaps you mean airspeed? The PDF mentioned (http://handle.dtic.mil/100.2/ADA399988) [1Mb] "The Influence of Ship Configuration on the Design of the Joint Strike Fighter" plus this PDF:
&
http://www.robertheffley.com/docs/HQs/N ... 002_71.pdf (2.8Mb) "REVIEW OF THE CARRIER APPROACH CRITERIA FOR CARRIER-BASED AIRCRAFT PHASE I; FINAL REPORT" make it clear I think that the 'visibility over the nose is important' but one of many other considerations - not the only one. Remember the pilot of a JSF (any kind) can look through the airframe to see everything all around, so amongst other things that FOV is less important compared to other variables.

Probably the first PDF mentioned above has best general info about JSF-C criteria considerations. Without someone publically explaining the issues in detail then we have not a lot to go on - but I'll keep looking because I'm interested. Yes the arresting gear limitation is crucial - dictating a lot. Probably the actual AoA detail is out there - it is just not easily found for the moment.

Did you get to use the FSX Accelerator A-4K KAHU yet? http://www.fratbrosdesign.com/ The KAHU HUD with AoA Indexer (like Hornet and freeware Dino Catteneo Goshawk T-45C and Tomcat F-14D show these Optimum AoA issues perfectly. :-)
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Unread post12 Jan 2010, 22:40

Spaz - with lower AOA I meant lower optimum approach AOA than the air force variant. For example the CV can have the usual 8 degrees, while the CTOL may have the more typical 11 degrees. With lower required AOA your nose will be lower, thus better visibility to the mirror and the deck. I am sure they will be able to see through the aircraft with the HMD, but what if the DAS fails...
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Unread post12 Jan 2010, 23:33

Yes, doing a manual approach without any fancy aids relying totally on 'meatball, lineup and airspeed [Optimum Angle of Attack]" is always good. :-)

One thing to consider is that likely the JSF-A carries some excess airspeed just before touchdown (unlike JSF-C) for the flare before touchdown on the runway. How you factor that in from whatever side views you have I have no idea. Perhaps if you can have identical viewpoints for the AoA just before the flare for the JSF-A and the 'just before touchdown' same view for the JSF-C then that would be helpful. However the JSF-C has not flown yet AFAIK. What the JSF-B does for a converntional approach and landing I have no idea but I guess because it is more similar to the JSF-A, the JSF-B will replicate the JSF-A conventional approach, unless we know otherwise, would be my uninformed guess. :-)

The side view is also important - looking down to the front and port side for that important half way from base turn to finals view of the carrier landing (and for long straight in approaches at night for example). Yet failure of critical aids in the JSF-C will be a real emergency most likely; necessitating other solutions. I wonder if the JSF-C will have an AoA indexer on top of all that fancy flat panel display gubbins?
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Unread post13 Jan 2010, 00:42

Haha, AOA indexer - no way :) You will have an AOA bracket on the HUD/HMD, well if that fails - then you must use pitch or just speed as reference 8)

BTW, from my own pictures in the beginning of the thread I calculated the AOA of the aircraft to be between 9.7 and 10.2 degrees. That's not necessarily the optimum AOA, nor is the visual calculation very precise, but it's a rough estimate.
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Unread post13 Jan 2010, 00:50

neutrino, why not a conventional indexer as a backup? You mention loss of flat panel screens already. I guess there would be an emergency flat panel display of some kind and I had not forgotten HMD but if there is going to be catastrophic 'instrument failure' then the AoA indexer would be a nice backup that all Naval Aviators would be familiar to use. Otherwise in normal landing I gather the HMD will have the indexer. Remember in ordinary use for a visual landing (without the HMD working) the AoA indexer would be in line of sight of pilot looking at meatball and lineup.

Whatever you reckon is Opt AoA is fine by me - until we know for certain. Most of JSF knowledge is guesswork for the moment (from the outside anyway). Maybe someone will see your message to at least tell you the AoA?
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Unread post13 Jan 2010, 06:18

spazsinbad wrote:Yes, doing a manual approach without any fancy aids relying totally on 'meatball, lineup and airspeed [Optimum Angle of Attack]" is always good. :-)

One thing to consider is that likely the JSF-A carries some excess airspeed just before touchdown (unlike JSF-C) for the flare before touchdown on the runway. How you factor that in from whatever side views you have I have no idea. Perhaps if you can have identical viewpoints for the AoA just before the flare for the JSF-A and the 'just before touchdown' same view for the JSF-C then that would be helpful. However the JSF-C has not flown yet AFAIK. What the JSF-B does for a converntional approach and landing I have no idea but I guess because it is more similar to the JSF-A, the JSF-B will replicate the JSF-A conventional approach, unless we know otherwise, would be my uninformed guess. :-)

The side view is also important - looking down to the front and port side for that important half way from base turn to finals view of the carrier landing (and for long straight in approaches at night for example). Yet failure of critical aids in the JSF-C will be a real emergency most likely; necessitating other solutions. I wonder if the JSF-C will have an AoA indexer on top of all that fancy flat panel display gubbins?


If those failures were to also effect the FBW computers, it wouldn't matter.
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Unread post08 Jun 2010, 00:00

Would be helpful if any AoA data for carrier landing is known but here is some more info from 1st flight comments:

"Handling with landing gear down was a key focus of the first flight as the F-35C has a 30% larger wing and uprated flight controls to reduce takeoff and landing speeds compared with the other F-35 variants. Knowles says the aircraft approached at 135 kt., compared with 155 kt. for the smaller-winged F-35A and B variants at the same 40,000-lb. gross weight. Takeoff rotation speed was 15-20 kt. slower, he says.
&
The 57-min. first flight focused on gear-down handling and formation flying with the F/A-18 chase aircraft in “an early look at handling around the carrier”, says Knowles, adding “The approach was very stable, with good roll response.” [http://alturl.com/fnsk]
RAN FAA A4G: http://tinyurl.com/ctfwb3t http://tinyurl.com/ccmlenr http://www.youtube.com/user/bengello/videos
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