Forum: F-35 Lightning II

Been wondering for some time now about any issues that could arrise if a pilot (hopefully would never happen) had to egress or eject from a F-35B in a hover above ground, say a few hundred feet or 1000 or so feet AGL with the lift-fan in the equation. Bottom-line, with the lift-fan sucking in air into its inlet (a lot) to maintain hover and the air inlet door facing forward, drawing in accelerated air directly over the pilot's canopy, if the pilot were to eject, would debris from the canopy get rapidly pulled into the inlet of the lift fan causing the aircraft to suddenly change position and/or could the mass flow intake into the lift-fan's assembly change ejection seat trajectory?

F-16.net Sponsor

Debris would likely get sucked into the lift fan, but if you're ejecting, you're already chucking the airframe in the trash anyway, so no worries there. As for the airflow changing the direction of the seat, I would imagine that the pulse of the seat's motor would be sufficient to blast through that airflow without it changing the trajectory since it's designed to counter up to a 600mph slipstream in forward flight.

Lightndattic wrote:

but if you're ejecting, you're already chucking the airframe in the trash anyway, so no worries there.

Unless you are the CAF. Our sqn color bird has two ejections and still flies missions daily.

I don't think that pilot is too concerned about debris getting sucked into the lift fan during an ejection.

Lightndattic wrote:

but if you're ejecting, you're already chucking the airframe in the trash anyway, so no worries there.

Not really, we had a few Harriers that had multiple ejections.

One aircraft had a birdstrike on T/O from a restricted field and went through the pine trees as the pilot ejected, we were able to tow it out after cutting down some of the trees.

Same aircraft had a flight control problem in the hover, pilot ejected, aircraft pitched nose down and had an arrival landing.

Next time the nose wheel steering failed and the aircraft ran off the runway, pilot ejected as the aircraft left the hardtop.

Last time the pilot ran off the deck, ended up in the safety netting and had to blow the canopy to get out.

Aircraft finished up in the training squadron and is now in the boneyard.

Just because you eject does not mean that the airframe is toast

I agree that it would be unlikely that debris being rapidly sucked-into the lift fan would cause the pilot from being able to eject, but it looks pretty close.
The fan door facing forward, drawing in cooler air from the forward section of the aircraft would protect it from drawing in hotter air from the rear, but a sudden failure of the lift fan would cause a large asymmetric force to be applied to the aircraft from the rear's lobster back exhaust nozzle assembly. I am sure Lockheed engineers ran calculations to determine the safety parameters required for a high probability of safe ejection while in the hover with the new lift-fan assembly such as, ejection sequence interval, acceleration of the ejection seat, debris intake effects timing, aircraft position etc... There is no doubt, that the design decisions made on the F-35B's STOVL design limit it to low speeds, unlike those employed on the Harrier. Nonetheless, it sure appears to be quite close...

asiatrails wrote:

Aircraft finished up in the training squadron and is now in the boneyard.

What the hell was the name of that plane? "3rd Time's the Charm"? "Three Strikes"?

Reminds me of the F-106 (58-0787) at Malmstrom. The pilot punched out in a flat spin. It landed in a snow bank, and after some repairs, lived to fly again.

Really jetblast, I don't see this ejection scenario occurring the way you are imagining.

If you are hovering, that means that the engine is still working as advertised.

It also means that you are likely at a low enough altitude to put it on the deck.

Also, at a hover, it would mean that you likely aren't having any flight control issues.

Now, if FCS issues arise while in a hover, you are probably going to see the aircraft quickly go out of control, at which point the pilot would initiate ejection.

My point? If it's hovering, that means it's still flying, and it's low enough to likely land safely. No reason to pull handles.

I agree; when you pull the "I'm outta' here" handles, you're hardly worried about FOD to the LiftFan or motor... Rolling Eyes

Keep 'em flyin' (safely) Thumb

TEG

TC wrote:

asiatrails wrote:

Aircraft finished up in the training squadron and is now in the boneyard.

What the hell was the name of that plane? "3rd Time's the Charm"? "Three Strikes"?

Reminds me of the F-106 (58-0787) at Malmstrom. The pilot punched out in a flat spin. It landed in a snow bank, and after some repairs, lived to fly again.

Really jetblast, I don't see this ejection scenario occurring the way you are imagining.

If you are hovering, that means that the engine is still working as advertised.

It also means that you are likely at a low enough altitude to put it on the deck.

Also, at a hover, it would mean that you likely aren't having any flight control issues.

Now, if FCS issues arise while in a hover, you are probably going to see the aircraft quickly go out of control, at which point the pilot would initiate ejection.

My point? If it's hovering, that means it's still flying, and it's low enough to likely land safely. No reason to pull handles.

I've heard of another F-106 at McChord AFB where the pilot ejected and the plane went on to a perfect landing and rolled slowly off the side of the runway with very little damage. It also was repaired and flown again.

You might be worried about FOD to the lift-fan assembly if you can not clear it, since you might be the FOD. There has been Harriers in normal hovers that within a few hundredths of a second went into an abnormal hover causing the aircraft to rapidly change attitude and position necessitating a very quick ejection. The point was that a catastrophic failure of a critical component within the F-35B's STOVL system would very quickly change a normal hover to an abnormal one. Even if the pilot managed to blast through the air intake stream tube if you will, of the lift-fan, his ejection seat *could* strike the lift-fan assembly's intake door; that is, the inability to clear it. Further, the jet in a STOVL (RVL) scenario at say 180 knots could make matters worse. I believe that the ejection seat's acceleration and rapidly expanding propulsion gasses should "break through" the lift-fan's air intake, but will the seat fully clear the assembly's intake door in all scenarios? Probably, but I am not 100% convinced. This is not a bashing of the F-35 in any matter, I really like the -35, BUT, there is no question in my mind that its STOVL mechanism as a whole is quite complex and has many points of failure inherent in it. Stuff like this bothers JetBlast:)

JetBlast16

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

Have you seen video of an ACESII seat doing it's work? There's no doubt in my mind the F-35's seat is going to pop the pilot clear of the aircraft without passing Go and without collecting $200.

jetblast16 wrote:

went into an abnormal hover causing the aircraft to rapidly change attitude and position necessitating a very quick ejection.

But that's not ejecting from a hover either. That's ejecting from an out of control aircraft with minimal forward speed, not unlike the Navy F-4 crew that punched out after takeoff at St. Louis.

With the speed the seat is travelling when it clears the rails (about 150 MPH, IIRC), the pilot would be well clear of the inlet danger area once he punches out.

Martin Baker designed the -16 with this type of ejection scenario in mind.

Guysmiley wrote:

Have you seen video of an ACESII seat doing it's work? There's no doubt in my mind the F-35's seat is going to pop the pilot clear of the aircraft without passing Go and without collecting $200.

I would happily put my full faith and trust in the performance of the people from Chalgrove and the spirit of Benny Lynch

jetblast16 wrote:

I am sure Lockheed engineers ran calculations to determine the safety parameters required for a high probability of safe ejection while in the hover with the new lift-fan assembly.........

That's probably why the STOVL version has a pilot selectable auto-ejection mode, which I think I read somewhere is primarily an inertially referenced system to detect the first indication of thrust loss or attitude control degradation. Pilot selection of this mode will probably be subject to a wide range of varying confidence levels in it...... until it works right (or wrong) once.

If the lift fan intake has any effect on the auto-ejection sequence at all, which is doubtful, it would have to occur after a number of pieces of the detonated canopy have been sucked into it and I would think the seat would be well clear by then. Some forward motion could be less than optimum, but I would doubt that the door would still be programmed open at 180 knots on takeoff.

Somebody's got to be first.

OL

(Not quite the problem the F-107 had)

outlaw162 wrote:

jetblast16 wrote:

I am sure Lockheed engineers ran calculations to determine the safety parameters required for a high probability of safe ejection while in the hover with the new lift-fan assembly.........

That's probably why the STOVL version has a pilot selectable auto-ejection mode, which I think I read somewhere is primarily an inertially referenced system to detect the first indication of thrust loss or attitude control degradation. Pilot selection of this mode will probably be subject to a wide range of varying confidence levels in it...... until it works right (or wrong) once.

If the lift fan intake has any effect on the auto-ejection sequence at all, which is doubtful, it would have to occur after a number of pieces of the detonated canopy have been sucked into it and I would think the seat would be well clear by then. Some forward motion could be less than optimum, but I would doubt that the door would still be programmed open at 180 knots on takeoff.

Somebody's got to be first.

OL

(Not quite the problem the F-107 had)

To give people an idea how fast things happen, I understand that the MK16 seat timing in Mode 1 is set for about 1.4 seconds from initiation to fully open and stable chute. This includes the canopy shattering, deployment of the seat stabilizers, deployment of the drogue chute and finally the main chute and seat separation.

Ejection mode identification (1 thru 5) is identified about 250 to 300 milliseconds after initiation.

jetblast16 wrote:

Been wondering for some time now about any issues that could arrise if a pilot (hopefully would never happen) had to egress or eject from a F-35B in a hover above ground,

You WILL see a few ejections from all models of the Lightning II. Like George Zimmer of the Men's Wearhouse always says:

"I guarantee it."

darkvarkguy wrote:

I've heard of another F-106 at McChord AFB where the pilot ejected and the plane went on to a perfect landing and rolled slowly off the side of the runway with very little damage. It also was repaired and flown again.

Really? I would have paid admission to have seen that.

Forum: F-35 Lightning II

F-35B Lightning II STOVL ejection in hover scenario