F-111 emergency landing with no wheel; what is done to reduce risks when loosing a wheel?

Question

There's an interesting incident described here about an F-111 that lost a wheel during take off.

Couple of questions:

1. What are the relative risks of an ejection vs a no-wheels belly landing. I mean obviously the costly loss of airframe. But is the risk to life pretty even odds?

   In a conventional aircraft (e.g. civillian) ejecting is just not an option so belly landings are the norm. But in an F-111 is a belly landing still safer than a controlled, planned ejection?

2. The film interviews the pilots & they say something to the effect of

"It's good that someone on the ground noticed. Otherwise we'd have tried landing without even knowing that we didn't have a wheel."

Are there no sensors etc. that'd detect they had lost a wheel? Any other indirect indications based on asymmetric drag, hydraulics etc. that one may expect? In other words, how likely is it that one loses a whole wheel but does not know.

3. Are there standard procedures where ATC uses binoculars etc. to check visually whether all seems OK with a landing aircraft (wheels etc.) I know they will check on request, but is there any standard protocol?

4. Don't military airfields lay down foam for emergency landings? Or is there a downside to foam on the runway?

Answer 1

What are the relative risks of an ejection vs a no-wheels belly landing. I mean obviously the costly loss of airframe. But is the risk to life pretty even odds?

In a conventional aircraft (e.g. civillian) ejecting is just not an option so belly landings are the norm. But in an F-111 is a belly landing still safer than a controlled, planned ejection?

1. Ejecting is an extremely violent event, often resulting in the pilot being removed from service for an extended time period, or permanently. 1 in 3 suffer back fractures or other major complications. Ejecting is possibly an end-of-career move for pilots (at best, an end-of-life one at worst). Belly landing on the other hand isn't usually a bad event, typically the aircraft is repaired and returned to service. In an ejection, the aircraft is a total loss, not to mention a rather large unguided bomb.

Are there no sensors etc. that'd detect they had lost a wheel? Any other indirect indications based on asymmetric drag, hydraulics etc. that one may expect? In other words, how likely is it that one loses a whole wheel but does not know.

2. No, there are no "wheel fell off" sensors. There are possible sensors to tell the pilot of low tire pressure, and certainly have sensors for hydraulic pressure. That isn't to say though that getting a low tire pressure means a wheels-up landing, landing on a flat tire is entirely possible. Drag probably isn't going to be significant, at least not enough to notice outside of gusts or other factors. That being said, having a wheel "fall off" is an extremely rare event, probably so few that you could count them by hand.

Are there standard procedures where ATC uses binoculars etc. to check visually whether all seems OK with a landing aircraft (wheels etc.) I know they will check on request, but is there any standard protocol?

3. Not typically, but ATC often watches departing aircraft with binoculars, not necessarily looking for missing parts though. In clear visual conditions, it would probably be pretty apparent that a wheel fell off to people on the ground, at the very least the next departing aircraft who had to avoid it on the runway. Usually when something falls off the aircraft, the runway needs to be closed while they do a FOD (foreign object debris) removal run.

Don't military airfields lay down foam for emergency landings? Or is there a downside to foam on the runway?

4. Yes, military airports can lay down AFFF (aqueous film-forming foam) on the runway, but you don't always need to. The down side is that it causes the aircraft to slide quite a bit further than it may be planned, and it's incredibly hard to clean out. If there isn't much of a risk of fire, its better to just belly it down in the grass. Or just let it slide on the runway. Most military aircraft can dump fuel and land without much fire risk.

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By the way, if you think it is impressive to belly-land an F-111 after a wheel falls off, you should watch this video about an Israeli pilot who landed an F-15 with one wing!!!.

Answer 2

1.What are the relative risks of an ejection vs a no-wheels belly landing. I mean obviously the costly loss of airframe. But is the risk to life pretty even odds?

Realities of ejection:

• Loss of a $30 million aircraft which is no longer in production
• Violent separation of crew capsule (F-111s have a detachable crew capsule as opposed to conventional ejection seats) and violent impact of capsule on landing, even with successful parachute deployment and can be amplified by terrain conditions at impact site eg jagged rocks, uneven ground, etc. This frequently causes injuries to the flight crew and should only be done if the alternatives to ejection pose a greater risk to life and limb.
• Aircraft has to be abandoned in such a manner that it will not hit people or man made structures on the ground. This requires ejecting over remote land areas or out at sea, creating a further impedance to rescue operations.
• Crash of abandoned aircraft and subsequent destruction by fire creates explosion and wildfire hazards, toxic chemicals and other risks to people and or wildlife around or approaching the wreckage.

Realities of a forced landing with undercarriage retracted:

• Difficulty and risk dependent on condition at landing site. Long stretches of smooth, hard surface pose minimal risk to the aircraft and crew, though it is quite a wild ride; this is why military flight test facilities like Edwards AFB and China Lake NAS are placed on or near ancient dry lake beds. Grassy fields with soft ground pose a greater risk as part of the airframe can dig into or snag the ground, tall grass, scrub, etc, violently yanking or possibly flipping the jet during slideout, increasing the risk of injury or death and the total loss of the aircraft.

• No matter how you do it, you're going to damage the underside of the aircraft during the landing. This will slough off the skin of the aircraft as well and grind down extended structures, frames and longerons, rupture fuel tanks and damage mission systems. That can be minimized with good airmanship and a smooth touchdown and controlled slideout. Nevertheless, there is a risk that the aircraft will still have to be written off.

• Belly landings increase the risk of FOD ingestion into the engines, damaging them and creating further risks to the aircraft and flight crew.

• Directional control the aircraft is seriously diminished or non-existent at slower speeds, creating a risk of the aircraft veering off and striking structures in the vicinity of the landing area.

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While the takeoff and wheel-loss event was not caught on film, I would take an educated guess that one of the main tires came loose from the aircraft just as it lifted off the runway and prior to the pilot commanding the retraction of the undercarriage. I'm sure it made for quite a sight for tower controllers watching this big tire come loose from the jet and go bouncing down the runway.

As for the flight crew all that can be done once they get the call is 1) Don't Panic 2) Fly the jet 3) A quick check of the cockpit instruments and warning lights indicates nothing else is wrong with the airplane; we have X pounds of fuel on board which should give about Y hours of flight time with conservative throttle settings. Let's get to a safe altitude to hold and see if we can work this problem out. We're missing a main wheel? - OK. What are the options? Probably either ejection or a belly landing. Neither the flight manual for the F-111 airplane nor ops knows or lists anything about attempting this sort of a landing. Based on all the scenarios as well as the USAF belly landing of an F-111 they had on file, the decision from both the flight crew and ground personnel the route of minimum risk was to attempt a gear up landing with the use of arresting gear to slow the jet down faster. So the flight crew sets up for a few low level, slow speed passes for practice while burning off fuel, then they make the attempt - and pulled it off with great success.

Are there no sensors etc. that'd detect they had lost a wheel? Any other indirect indications based on asymmetric drag, hydraulics etc. that one may expect? In other words, how likely is it that one loses a whole wheel but does not know.

Wheels coming loose from an aircraft like that is such a rare contingency that no such warning system has ever been considered for that. There are landing gear position lights in the cockpit to indicate whether the landing gear is extended properly (down and locked) for landing. There is also a Weight on Wheels (WoW) pressure switch on the landing gear itself to sense if there are structure loads being applied to the landing gear in order to lock out systems which should not operate when the aircraft is on the ground ie landing gear retraction, weapons, etc.

3.Are there standard procedures where ATC uses binoculars etc. to check visually whether all seems OK with a landing aircraft (wheels etc.) I know they will check on request, but is there any standard protocol?

Not on landing, but @RonBeyer's answer suggests that it's not uncommon for ATC to watch departing aircraft. It's easier to notice things falling off than to notice their absence, and spotting FOD on runways is important.

As I said before this kind of incident is so rare it's not even thought of. I'm guessing it came as quite a shock to the controller watching what should have been another typical Aardvark departure, then see what appears to be the wheel come off and go bouncing down the runway.

Answer 3

The F111 uses an ejection capsule, not individual ejection seats. Basically the entire cockpit separates from the rest of the aircraft. It requires 3 parachutes to safely let the capsule down. failure of even 1 parachute can result in a unsurvivable landing.

I would think a belly landing would be safer.

Answer 4

Stay with the airplane

I did have a squadron mate who was leading a flight in the break and accidentally switched off guard on his radio in the turn downwind. Unfortunately for him, his radios were also on the wrong frequencies, and he missed the fireworks display set off by tower at the approach end of the runway. He landed gear up and he told me later that it was a bit noisy, but the aircraft slid to a stop. "It was a sickening feeling," he said, "when you know you should be touching down but are instead sinking through ground effect." He knew something was up, just couldn't figure out what. So landing with both gear up doesn't sound too bad to me, and better than an ejection. I would be interested to know if anyone has heard of taking the gear at the end of the runway in such a case?

I have known a pilot who took an ejection over the ocean after a mid-air in an ACM (dog fighting) engagement. He was flying within a week, and, although the accident investigation found him accountable, he remained in the Navy as a pilot. I don't know if it precluded him from being selected for CMDR. It certainly could not have helped.

At sea you try to get aboard the ship and stay out of your chute, especially true if it is dark out. Even a controlled ejection at sea is risky. Instantaneous G's in the A7E ejection were 40, which is enough to make you lose consciousness during that phase. There is a burnout phase of 20 G's. It is a 0-0 capable ejection seat, which means it will give you a swing or two in the chute if you eject at 0 altitude and 0 airspeed. Generally speaking, the envelope of the seat, or when can you can safely eject given your descent rate versus airspeed, is complicated and I don't remember having any quick way of knowing when it was safe to eject. There were points on the envelope that we memorized. For example, an ejection over 400 knots can dislocate legs and arms, not necessarily in that order. Most of the accident investigations I read, where an uncontrolled ejection was attempted, the pilot initiated outside the safe envelope of the seat. Pilot's like to stay with their aircraft.

Each emergency is evaluated by the pilot, and then, if time permits, maintenance and the skipper, after which a course of action is determined. All of these things factor in to a decision to stay or eject.

Over water your troubles are just beginning when you are in the chute. Once you gain consciousness you have to prepare for water entry. There is a possibility that you can get entangled with the shroud lines. The parachute also is a great sea anchor, and will drag you under. The procedure was to release your Koch fittings when the raft hit the water. The single person raft held your survival gear and was deployed from beneath your seat. It was on a 14 foot tether. To give you an idea of some of the risks you might not consider. My squadron mate hit the water, which was at around 60 degrees Fahrenheit, he was in a wet suit and wearing his Nomex flight gloves. By the time he got to the raft and tried to haul himself in, his hands were numb and useless. He had considerable difficulty just getting into the raft, let alone then using the emergency radio to coordinate with the rescue aircraft and helicopters.

By the way, the other plane in the mid-air lost the section of wing from the joint outward (basically the whole wing), where the aileron was located. Three redundant hydraulic systems maintained the hydraulic flight control system. He stayed with the aircraft and eventually was diverted to Crete where he did an emergency landing. Again, it is worth pointing out that there was no ejection even in this case. There was also plenty of time to talk with maintenance, test the flight characteristics of the aircraft near gear down speed, evaluate the situation, and decide the safest course of action.

The point is, as a pilot I always wanted to stay with the aircraft as long as I could. In fact, the only "standing" controlled ejection procedure I heard discussed was the case where you run out of fuel at the ship. They steer you to some location, where the rescue has been coordinated and you eject.

Use the net

With a missing strut or wheel the standard procedure on the ship is to take the barricade. I was covering the last recovery as a hot tanker. I was in my A7E with a buddy store and 2,000 pounds of gas to give away. The designated tanker was an A6 circling at 5,000 feet, I was turning and parked right on the foul line near the Island. If the airborne tanker went down for some reason, and couldn't fulfill its mission as tanker, I would replace it taking quick cat shot off the bow.

I was up departure on one radio, and listening to approach on the other. The last aircraft coming aboard was AJ501, an A6. I heard the pilot's initial call of "Alpha Juliet 5-0-1, ball." The LSO had a welcoming tone to his voice when he calmly responded, "Roger ball, a bit left for line up." I was sitting on the foul line and watching the approach. I heard the LSO's call for lineup, but watched the A6 drop its right wing, which was pretty closely followed by another less welcoming call for "Left for line up!" from the LSO. The driver of the A6 dropped his right wing again and was now in close.

I just sat there as he boresighted me on the foul line. Didn't reach for my ejection handle between my legs, just watched with my eyes wide open. Incredulous of what was happening. It never got past my eyes into the working part of my brain. The LSO sounded downright rude on his last call with "LEFT FOR LINEUP! WAVE OFF! WAVE OFF!" Even today I shiver at the call. The pilot reached enlightenment at that point, with me a close second, as he dropped the left wing hard with the ball going off the top of the mirror. There were probably some power calls in there as well, I don't remember. It was a very big correction to centerline with military power coming back on the jet, and the A6 impacted the deck on its left strut, which subsequently snapped off and skipped, sparking its way down the deck with a high final arc to its trajectory as it disappeared into the night sea. Power was at military and the aircraft boltered.

I don't remember if they went and got some gas, but the pilot had time to collect himself because they had to prepare the barricade. There is a good scene in the movie Top Gun where an A7E takes the barricade, and shows the crew raising the pylons. The barricade is basically a big net strung between pylons that are raised up out of the deck on either side of the landing area. The critical point for the pilot is that the top of the barricade, that suspends the net, is a wire cable that is capable of cutting the airframe in two if the net is missed on a high approach.

The aircraft returned, for probably the pilot's most difficult approach of his career. The LSO will make the approach window smaller due to the risks involved, meaning that the aircraft will be held to smaller differences from speed and glide path and waved off earlier in the approach. It was a perfect barricade landing.

Answer 5

I also imagine when the landing gear fell off it may had caught the ATCs or another's attention, then directing to the ATC, upon impact or on one of the bounces of hitting the dirt and throwing up a cloud.

Maybe a bit off topic but I believe most military and larger domestic aircraft have the ability to release fuel. So prior to landing they would also release majority of fuel to reduce the weight of the aircraft.