F-35 pitch authority at very low speed

The F-35 compared with other modern jets.
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gta4

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Unread post23 May 2018, 13:31

https://www.youtube.com/watch?v=J2Be50SNlSQ
https://www.youtube.com/watch?v=w87AvnDiVBU
Some non thrust-vectored jets can do tail slide. Normally it cannot level nose up immediately after the maneuver, because low airspeed does not generate sufficient pitch moment. Their aerodynamic control surfaces require enough airflow to be effective. They need to dive long time, in order to get sufficient speed to pull the nose up.

However, the F-35 may be different:
https://youtu.be/aWji8AcOYGA
At 0:10 s F-35 does a tail slide. It starts with almost zero airspeed, and it levels its nose immediately. The pitch authority is exceptional. It seems that it could generate enough pitch moment even at low airspeed. Its aerodynamics surfaces are highly effective.
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sprstdlyscottsmn

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Unread post23 May 2018, 14:12

It still falls a thousand feet before recovery, but yes. The long chord of the stabs helps bite the air at lower dynamic pressures. Longer chord means increased Reynolds number.
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marsavian

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Unread post23 May 2018, 18:21

Its spin recovery is very graceful and safe. The proof is in the pudding, none have been lost so far.

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citanon

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Unread post24 May 2018, 02:33

My pet theory, which I spouted in the F35 Paris thread, is that the rearward positioning of the rear horizontal stabs relative to the engine nozzle allows the engine exhaust to actively draw air over the stabilizers via aerodynamic entrainment (not sure if I'm using this term right).

In effect, this aero configuration gives the F35 similar benefits to thrust vectoring without actually using swivelling engine nozzles.

Also, take a look at the shape of the belly.

Image

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It's probably not unreasonable to suspect that the shaping helps channel airflow towards control surfaces in high angle of attack situations.
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krorvik

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Unread post25 May 2018, 19:19

I love that hypothesis. Devil is in the details.
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Unread post25 May 2018, 19:56

.WEBP images doan GROK here so converted to JPG then cropped it as shown below.
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citanon

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Unread post26 May 2018, 02:21

spazsinbad wrote:.WEBP images doan GROK here so converted to JPG then cropped it as shown below.


Thanks!
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steve2267

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Unread post26 May 2018, 14:25

An interesting photo that came across the F-35 twitter feed.

I am guessing this image shows rear stabs at max deflection, or close to it:

F-35_stabs(twitter-DeAoR7hV4AA6kRk).jpg
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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sferrin

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Unread post26 May 2018, 15:44

spazsinbad wrote:.WEBP images doan GROK here so converted to JPG then cropped it as shown below.


Always thought that image looked awesome for a Sci-Fi bomber. Imagine what you're seeing is the top the aircraft and the Chin EOTS is the cockpit area.
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citanon

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Unread post26 May 2018, 22:13

sferrin wrote:
spazsinbad wrote:.WEBP images doan GROK here so converted to JPG then cropped it as shown below.


Always thought that image looked awesome for a Sci-Fi bomber. Imagine what you're seeing is the top the aircraft and the Chin EOTS is the cockpit area.


Great, now I can't unsee it :wink:

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