Forum: General

Hi guys, don't know if you have seen this before; certainly a smart piece of work getting her back on the ground!

http://www.youtube.com/watch?v=9CrY8gsu7do&feature=related

Andy

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Thanks for videos, boff180. I was there for both scenes.

It may not be obvious, but the takeoff and landing are from two different events. The takeoff is Flight "0" of YF-16 No. 1 at Edwards AFB (January 1974). The landing is at Fort Worth (Carswell AFB) following a practice demonstration flight of YF-16 No. 2 (May 1975). The airplane was due to depart for the Paris Air Show and a tour of several other European bases. No. 1 was quickly flown in from Edwards and made the trip to Europe. The tour was highly successful and paved the way for four NATO nations to select the F-16 for their air forces.

No. 2 was repaired and returned to the flight test program at Edwards.

The narrator of the videos was Neal Anderson, GD test pilot, and a good friend.

Elite Joined: Jan 14, 2004 Posts: 2444 Status: Offline

Perhaps someone with some flight test experience could answer this one, but why didn't Neal Anderson blow the gear down, and try to land that way. With the engine off, I'm not sure that he'd have brakes, but Carswell does have a long runway. Was there a reason why this landing method was not possible and/or not attempted?

I can tell you exactly what happened. A new demo routine was planned for the Paris show, which included a right 270 degree roll, hard pull to the left immediately after lift off as the gear was coming up. I assume you are familiar with the multi-axis rotations the gear goes through to retract. Normal gear extend/retract is at near zero roll rate.

The day before the incident, Neal flew the demo without any problems. However after the flight, a bracket in the wheel well was found to be broken off its mount. Well, we can't have that. so let's beef up the bracket. The next day, same thing happened (surprise, surprise) except with the beefed up bracket did not fail, but jammed the gear so it would not go up or down. Neal tried high g and full rolls to dislodge the gear but no help. Time was running out, as there was a low fuel load (airshow!). Carswell had a tanker at last chance ready to takeoff, but was not allowed to as it was overloaded to a "war only" takeoff weight. So Neal landed with 5 gallons of fuel.

I'm guessing he tried to blow the gear down, but it would not have worked anyway. The normal system was working fine, just did not have the power to overcome the jam. The emergency system has no more capability than the normal, so it wouldn't work either.

So why did it jam? Remember the multi-axis rotation? The added roll maneuver at takeoff gave the spinning wheel yet another axis of rotation, and the added gyro and centrifugal forces displaced the gear enough to contact the bracket. The right gear door did not close, since it is signaled to close by the gear uplock sensor, and the gear never got that far. So Neal flew about half the demo with the door open before knocking off.

In the -1 list of prohibited maneuvers, there is one which says no roll rate during gear retraction. Guess why.

If Neal could have blown the gear down, there would have been no need the shut down the engine. Even with engine shut down, brakes still work, either from accumulators or the MEPU. And there is always the hook.

Elite Joined: Jan 14, 2004 Posts: 2444 Status: Offline

Interesting stuff. I've wondered for a long time why events transpired the way they did. More stuff that you knew you could have answered on f-16.net, but were afraid to ask.

johnwill wrote:

In the -1 list of prohibited maneuvers, there is one which says no roll rate during gear retraction. Guess why.

Hence, why the Thunderbirds do not copy the Blue Angels' "Dirty Roll" on takeoff. Now I know why I've never seen that done.

Every time I see that landing I'm amazed that, with the way the jet was bouncin' around, the lower lip of the intake didn't bite into Terra Firma and send Neal a$$ over tea kettle. Not Worthy

The incident happened in May, rainy season in Fort Worth. So the Terra was not quite so Firma. Left a nice furrow, and some dirt did get into the engine. The left wing tip AIM-9 did bite into the ground and broke the launcher and a small section of the outer leading edge flap. Of course, the ventrals departed the airplane and the right gear door (still open) was damaged.

Neal owned some private airplanes, and when he next applied for insurance, they increased his rates for having made a wheels up landing.

Elite Joined: Jan 14, 2004 Posts: 2444 Status: Offline

Neal Anderson was an excellent pilot, and that was an impressive display of airmanship on his part. Facing a situation where others might have been primarily concerned with saving themselves, and getting the jet down in any condition, Neal elected to save the jet to the best condition possible, and walk away from it (albeit, he was running as soon as he raised the canopy...can't say that I blame him there. Wink

)

If that had been an operational bird, you can bet that it would've flown again. I've seen much uglier Class As from the Viper fleet that have been returned to flying status (79-0377, aka, "Twice as Nice", anyone?).

Salute!

Hey, John-boy! I thot the only thing the air bottle did on the early Vipers was get the nose gear down. The gear handle and/or "apple" we pulled simply unlocked the main doors and the wheels "fell out" and/or were pulled out by air pressure.

In short, we needed hydraulics to get the gear up, but only God's gee to get them down, except for the nose gear.

Hence, when I had ice crystals in the actuators one day ( hydraulic contamination), I had the nose gear down and one main. Doors were all open. So I pulled a sh&%* pot full of gee and the lame main slammed down. Landed, but couldn't taxi back as hydraulic fluid was spraying all over the de-arm area. I had blown some seals on the lines, but big deal.

The Ft Worth deal was different, as you say. Mechanical jammed stuff is hard to correct.

later,

Gums sends ....

Gums, I think you are right about the blow down for nose gear only. I purposely didn't get too specific about the emergency system, 'cause I wasn't certain I remembered exactly how it worked. I was thinking the bottle unlocked the doors and the main gear uplock, and everything fell open due to God's g and airstream flow. The nose gear had to be forced open as you say, because the airstream prevented it from falling all the way down.

On Neal's first flight in No. 2 the nose gear would not extend fully due to a rigging problem. Gear swings on the ground were fine, but with 170 kt of air flow, it wouldn't downlock. He tried many things to no avail, and finally for no logical reason, hit the alternate flap switch. That evidently caused a small hydraulic pulse which pushed the gear forward just enough to downlock it. The ground crew re-rigged everything overnight, and he flew it again the next day. Same thing happened again, no nose gear green light. The same alternate flap switch trick worked again, landed normally, but that was the only time I ever saw Neal angry - maybe a little more than angry.

I have never understood his decision to land on the grass. I think he was fortunate not to flip it.
But, he walked away, the jet was repaired, so I guess you could say he made the right decision.

The choice was based on not having enough time to foam the runway. It was thought that the fire hazard was higher on the bare runway.

Newbie Joined: Apr 09, 2008 Posts: 1 Status: Offline

That's the first time I think I've seen the actual landing. Growing up, my father, who was an aeronautical engineer that worked on the development of the F-16 (I loved visiting Carswell with him as a kid to check out the planes Smile

), always used to say that the test pilot probably saved the company about a billion dollars and the project by landing it and not simply dumping it. Maybe he was exaggerating a bit, but to this day, he still has a bit of a "Wow! Thank goodness! How did that guy manage that ..." about the whole event.

Newbie Joined: Apr 10, 2008 Posts: 8 Status: Offline

Don't forget that the aircraft involved was YF-16 #2, which differed greatly from the FSD F-16 or Production F-16. The YF-16 did not have wheel pre-braking, but the FSD and Production versions do. On all but the two YF-16 aircraft, part of the hydraulic pressure that is retracting the MLG is also ported to the brakes, to stop the wheels from spinning as retraction commences. Without that feature on the YF-16, the gyroscopic effects of retracting the spinning MLG wheels while rolling the aircraft produced enough deflections to jam the right MLG in the well.

Right, tinkicker, pre-braking helps by eliminating the gyro loads, but the airplane roll also causes centrifugal loads which pull the gear out of position and could cause a jam. So rolling during retraction was still prohibited.

And pre-braking has unintended consequences, like brake pad wear and extra torque cycles to increase fatigue on the gear. No free lunch.

nbb1, who's your daddy? I might know him.

Forum: General

Early development YF-16 crash on YouTube