Honda jet crash KFFZ, 5 fatal

Pilot Fighter said:
When you are calculating contact PSI, tire PSI is not a factor.

Pressure = Force/Area^2

You could triple the tire psi and it doesn’t affect the contact psi if contact area doesn’t change. The force is the mass of the aircraft.

Where it could matter in an EMAS is if there was a curb at start of the EMAS pad to initiate a plowing effect.

With winter tires, you may want to increase contact psi, so skinnier tires, less contact area. The tire must carry a sufficient tire pressure to carry the load. The constraint is reducing contact area also reduces traction, so it’s an optimization problem.
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SteveC said:
It’s obvious that you don’t understand the difference between tire pressure and contact pressure when you post this:

Higher tire pressure, in and of itself, does not increase contact pressure. It’s the “skinnier” part that increases contact pressure, not the air pressure inside the tire.
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Guess you're never driven off road.
(like REAL off road, not driving on smooth dirt to get to the country club)

Don't believe me?

Find a bicycle with slick tires (easier to measure)
Pump tires to 60PSI
Get on the bike
Have someone draw an oval line where the tire contacts the ground.
Measure area: A=πab
Reduce to 30 PSI
Draw another oval
Measure again.

The air in the tires supports the plane. The tire supports the air.
Lower the pressure, the tire will deform to increase the contact area.

PSI x area MUST equal the weight of the aircraft.

Unless you're levitating.


(Note, this IS distorted slightly by certain ply structures, but this does NOT make them immune to physics)
 
DropTank said:
Guess you're never driven off road.
(like REAL off road, not driving on smooth dirt to get to the country club)

Don't believe me?

Find a bicycle with slick tires (easier to measure)
Pump tires to 60PSI
Get on the bike
Have someone draw an oval line where the tire contacts the ground.
Measure area: A=πab
Reduce to 30 PSI
Draw another oval
Measure again.

The air in the tires supports the plane. The tire supports the air.
Lower the pressure, the tire will deform to increase the contact area.

PSI x area MUST equal the weight of the aircraft.

Unless you're levitating.


(Note, this IS distorted slightly by certain ply structures, but this does NOT make them immune to physics)
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I’ve raced rallies in Saudi Arabia, if you don’t understand how tires work, you aren’t going to get far. I raced in the RWD class, very challenging to avoid getting stuck in the red dunes that have a consistency of powdered sugar.

That said, you’ve changed the subject. You now want to talk about contact psi, which I covered.

The subject was EMAS and you suggested that tire PSI mattered, it doesn’t. Contact PSI matters. If the contact area remains the same, the contact PSI stays the same. Yes, if you deflate a tire you increase contact area and reduce contact PSI.

A 100psi tire and 1000psi tire could have the same contact PSI.
 
Pilot Fighter said:
I’ve raced rallies in Saudi Arabia, if you don’t understand how tires work, you aren’t going to get far. I raced in the RWD class, very challenging to avoid getting stuck in the red dunes that have a consistency of powdered sugar.

That said, you’ve changed the subject. You now want to talk about contact psi, which I covered.

The subject was EMAS and you suggested that tire PSI mattered, it doesn’t. Contact PSI matters. If the contact area remains the same, the contact PSI stays the same. Yes, if you deflate a tire you increase contact area and reduce contact PSI.

A 100psi tire and 1000psi tire could have the same contact PSI.
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You're wrong, and I'm done explaining it to you.
 
DropTank said:
You're wrong, and I'm done explaining it to you.
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You appear to understand contact PSI now. However, please explain what tire pressure has to do with EMAS. EMAS doesn’t care about tire PSI.

In your post, you said a tire would punch through EMAS because of its high tire PSI. That’s wrong. Now, you want to keep posting about contact PSI, which I succinctly described a few posts ago.
 
Pilot Fighter said:
You appear to understand contact PSI now. However, please explain what tire pressure has to do with EMAS. EMAS doesn’t care about tire PSI.

In your post, you said a tire would punch through EMAS because of its high tire PSI. That’s wrong. Now, you want to keep posting about contact PSI, which I succinctly described a few posts ago.
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And regardless, at the speed the jet was moving at reaching the departure end of the runway, it still would’ve raced both over and partly through an EMAS bed, whether standard or modified length, through the chain link fence and ended up at or nearly at where it did end up.

All moot anyway, as there was no EMAS present; and I don’t see the city investing in one for the low amount of jet traffic that field gets.

All that said, I don’t see what the city could’ve reasonably done to prevent a very high speed abort like this, from going where it’s going to go once it exits the pavement.
 
Pilot Fighter said:
You appear to understand contact PSI now. However, please explain what tire pressure has to do with EMAS. EMAS doesn’t care about tire PSI.

In your post, you said a tire would punch through EMAS because of its high tire PSI. That’s wrong. Now, you want to keep posting about contact PSI, which I succinctly described a few posts ago.
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That's nice dear, continue to be wrong....

I know it burns you up....
 
DropTank said:
That's nice dear, continue to be wrong....

I know it burns you up....
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Continue to embarrass yourself. It’s interesting that you are distancing yourself from your first post about tire pressure and proceeding to explain contact PSI after I had done so.

Sure, inflating or deflating a tire affects contact area and consequently, contact PSI.

You said something silly about a 200 psi tire easily penetrating the EMAS surface. Now, you don’t want to talk about it.
 
MikeD said:
I expect that there might come to be some restriction or even prohibition on jet fixed wing ops coming.
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And somebody will sue, and the city will lose that lawsuit.

FAA requires equal access. If they can demonstrate that the airplane has the performance, then the FAA will rule “no basis”.

We had a field around us spectacularly unsuited for jet ops. Guy wanted to fly his jet in there, city said no. Sued and won.
 
Richman said:
And somebody will sue, and the city will lose that lawsuit.

FAA requires equal access. If they can demonstrate that the airplane has the performance, then the FAA will rule “no basis”.

We had a field around us spectacularly unsuited for jet ops. Guy wanted to fly his jet in there, city said no. Sued and won.
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Agree in principle, however Airports restrict and prohibit all kinds of ops all the time. Look at how many airports don’t allow touch and goes, or pattern work after certain hours, or restrictions to helicopter ops etc. while I don’t agree with all of those, they do come in various flavors at different places.

If the airport can’t make a restriction for safety, the city should be held harmless from an accident that they had no control over, by an aircraft that had the performance to operate in normal ops on the runway. Worse, if it didn’t, then the city truly should have no liability. The city isn’t responsible for a pilots decision to abort a takeoff at high speed for unknown reasons, on an extremely short runway.

Long range, this kind of litigation is the kind of thing that gets airports eventually closed down. Especially if they begin costing the city for massive liability payouts.
 
MikeD said:
Agree in principle, however Airports restrict and prohibit all kinds of ops all the time. Look at how many airports don’t allow touch and goes, or pattern work after certain hours, or restrictions to helicopter ops etc. while I don’t agree with all of those, they do come in various flavors at different places.

If the airport can’t make a restriction for safety, the city should be held harmless from an accident that they had no control over, by an aircraft that had the performance to operate in normal ops on the runway. Worse, if it didn’t, then the city truly should have no liability. The city isn’t responsible for a pilots decision to abort a takeoff at high speed for unknown reasons, on an extremely short runway.

Long range, this kind of litigation is the kind of thing that gets airports eventually closed down. Especially if they begin costing the city for massive liability payouts.
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Restrictions aren’t prohibitions. Restrictions are sometimes tossed out by the Feds as violating equal access, prohibitions almost always are.

Yes, that does lead to closures when the locals figure out they can’t win.

And yes, this is why we can’t have nice things.
 
Richman said:
And somebody will sue, and the city will lose that lawsuit.

FAA requires equal access. If they can demonstrate that the airplane has the performance, then the FAA will rule “no basis”.

We had a field around us spectacularly unsuited for jet ops. Guy wanted to fly his jet in there, city said no. Sued and won.
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Mira Slovak used to fly an L-29 (I think it was an L-29, it might've been some other Soviet airplane but it was absolutely a jet) out of Santa Paula occasionally. It was always very exciting, he'd taxi out with barely any fuel in the tanks and go off into the dirt off of the end of the runway and then turn around to get back onto the very edge of the pavement and then give her the beans. It always looked like it'd never get off the ground but it always did, it might've missed the berm off the other end of the runway by 6' but it always flew, of course it flew directly to Camarillo because it was just about out of fuel when he started it up. It was the sort of thing that would bring people out of their hangars to witness. I have no idea if the FAA even knew he was doing it, it was a different time and Santa Paula was/is a special place. Not to mention Mira was an aviation legend and a very nice person every time I ever interacted with him.
 
knot4u said:
Mira Slovak used to fly an L-29 (I think it was an L-29, it might've been some other Soviet airplane but it was absolutely a jet) out of Santa Paula occasionally. It was always very exciting, he'd taxi out with barely any fuel in the tanks and go off into the dirt off of the end of the runway and then turn around to get back onto the very edge of the pavement and then give her the beans. It always looked like it'd never get off the ground but it always did, it might've missed the berm off the other end of the runway by 6' but it always flew, of course it flew directly to Camarillo because it was just about out of fuel when he started it up. It was the sort of thing that would bring people out of their hangars to witness. I have no idea if the FAA even knew he was doing it, it was a different time and Santa Paula was/is a special place. Not to mention Mira was an aviation legend and a very nice person every time I ever interacted with him.
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This isn't meant to be insulting, but I have found over the years that mech's perceptions of what aviators are doing with airplanes is wildly out of touch with reality. The worst person imaginable to interview for an accident investigation would be mechs. I'm not saying you didn't see what you did, but what you wrote is exactly how one of my maintainers would describe a completely normal takeoff on any given day with nothing sketchy actually going on. It is both confusing, and also confusing. I'd also add that the stories become more and more unbelievable at an exponential rate, depending on how much they like you......which is to say, if they like you, you did the most insane impossible thing ever. Because you are sky god I guess. Don't hate me, it's a real phenomenon.
 
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///AMG said:
This isn't meant to be insulting, but I have found over the years that mech's perceptions of what aviators are doing with airplanes is wildly out of touch with reality. The worst person imaginable to interview for an accident investigation would be mechs. I'm not saying you didn't see what you did, but what you wrote is exactly how one of my maintainers would describe a completely normal takeoff on any given day with nothing sketchy actually going on. It is both confusing, and also confusing. I'd also add that the stories become more and more unbelievable at an exponential rate, depending on how much they like you......which is to say, if they like you, you did the most insane impossible thing ever. Because you are sky god I guess. Don't hate me, it's a real phenomenon.
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I'm not insulted and I understand your point. While I have great admiration for Mira what he was doing (operating a jet out of Santa Paula) was very risky and everyone knew it, other pilots, mechanics, the serving staff at the restaurant, everyone would come out to watch. I never stood at the departure end to measure his clearance from the nearest obstacle, but I talked to someone who did that gave me that estimate. This is the runway he'd use...

 
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