Lockheed: Many F-35B landings won’t be vertical

[bjr1028]

http://www.dodbuzz.com/2011/06/07/lockheed-many-f-35b-landings-wont-be-vertical/

Lockheed: Many F-35B landings won’t be vertical

By Philip Ewing Tuesday, June 7th, 2011 2:49 pm

A Marine Corps photo set this week shows a squadron of veteran AV-8B Harriers at work in Afghanistan supporting troops on the ground, and it brought to mind one of the capabilities the Marines’ F-35B Lightning II will have that the Harrier doesn’t. Everybody knows that the B can “transform,” like a Decepticon, for short takeoffs and vertical landings on Navy amphibious ships at sea. But unlike a Harrier, the B also can land like a conventional airplane, said Lockheed Martin vice president Steve O’Bryan at the company’s big media day last month.

So what, you might say. Well, the Harrier doesn’t land conventionally: Every time it comes back, even to a ground base, it needs to do a vertical landing or a rolling vertical landing, O’Bryan said, burning fuel and working its jet nozzles more or less the same way. But if a Lightning II pilot wants to, she’ll be able to land down a runway like a normal fighter jet, without engaging the lift fan or all those other ports and hatches and bells and whistles.

If many — or most — of the flights that a fighter makes over its life are not under operational circumstances, because pilots are training or ferrying their jets, that could mean that a typical B won’t need its vertical landing capability most of the time.


“I don’t want to speak for the Marine Corps, but as we do analysis for the STOVL variant, [we think] most of the landings will be conventional landings — you can come back and land on a normal 8,000-foot airstrip without stressing all those components,” O’Bryan said. “Of course it’s up to the operational units, but why would I stress those if I don’t have to? … That is an option that’s not available on the current generation of STOVL airplanes.”

Makes a lot of sense. Operating conventionally puts less strain on the aircraft and saves money on fuel and ordnance.

[aaam]

http://www.dodbuzz.com/2011/06/07/lockheed-many-f-35b-landings-wont-be-vertical/

Lockheed: Many F-35B landings won’t be vertical

By Philip Ewing Tuesday, June 7th, 2011 2:49 pm

Makes a lot of sense. Operating conventionally puts less strain on the aircraft and saves money on fuel and ordnance.

You know, that may not be completely certain. Not really sure if landing on and then rolling down a runway and then taxiing back (we'll ignore carrier type landings which put a major strain on the aircraft) is significantly less stressful than just settling down and taxiing a much shorter distance to park. On takeoff, the STO won't use more fuel than a CTO, and is there any data that indicates a conventional pattern and landing uses a lot less fuel than a VL approach and landing (even allowng for the higher power setting at the very end of the VL). Ordnance-wise, if the plane meets its bringback requirement, it's not much of an issue. The exception would be if the aircraft had to return soon after takeoff, when the STOVL might have to dump some fuel--but then so would a heavily loaded CTOL.

[mor10]

The Harrier can make a fully conventional landing, it's just they usually don't bother. Partly because the vertical landing doesn't really put that much excess load on the a/c, and arguably uses less fuel. Also, the Harrier is trickier to land than the F-35B will be, so just like with Navy CTOLs, practice, practice practice.

I don't see how an airplane that has to land under full power can use less than one that sails in on close to idle trust. How do you explain that?

[spazsinbad]

There are fair comments made about less ENGINE wear and tear - very high power vertical landing - compared to a lower power conventional landing. I think that is the point of the original article. Yes there is other mechanical wear and tear for longer taxi times but less relevant I would suggest. I guess more chance for taxi accidents also perhaps. Engine 'wear and tear' is going to be monitored as part of the 'health program' for the F-35B so I guess soon enough there will be statistics about what is good and what is not.

lamoey, I'm puzzling over your question: "I don't see how an airplane that has to land under full power can use less than one that sails in on close to idle trust. How do you explain that?"

IMHO I think there is misunderstanding about why a vertical landing is carried out by the Harrier at the end of a sortie. It is one way to retain currency for vertical landings on a flat deck. However as described 'running landings' are carried out but they are not really 'conventional landings' because as explained perhaps earlier the Harrier is not designed for that whereas the F-35B is (with nice tricycle undercarriage).

And yes a Harrier 'running landing' is tricky so unless necessary they are usually not performed - I'm guessing that Khandahar is an exception perhaps, whereas the crash there showed how 'tricky' they are especially with a load of ordnance. "Ya pays ya money and ya takes ya chances." I guess bringing back cheap bombs via a 'running landing' is useful if you only lose a Harrier every now and then? Some might argue that a vertical landing is not so easy but it is if practiced regularly AFAIK. So why not keep in practice using vertical landings? I don't make those decisions.

[mor10]

What I meant was that a Harrier lands under close to full power, while a conventional landing is more or less a glide, under the right circumstances. Some of the talk above indicates that the harrier may have to fly around until it is around 500lbs on fuel left before it can land, but in any case it would be burning a lot the last few minutes anyway. Also if a Harrier is anything like a helicopter, the ware and tear is by an order of magnitude higher during hover, so a lot of components may have much shorter survival time if hover is used a lot. A normal landing for an F-35B, on the other hand, depending on the priority and queue on final, may be a controlled glide all the way from operational altitude, without that much fuel consumption.

[spazsinbad]

lamoey, jet pilots manage their fuel to land with what is appropriate. There are several methods to do it but if less time airborne is a feature or they have to make a definite landing time "Charlie" as in a carrier landing then they will dump fuel if there is too much at time of intended landing (usually at max. landing weight in all cases because one never knows when fuel is required at last minute - I'll post a link to a barricade landing where the Hornet pilot lands with 300 lbs of fuel - phew - and he has a good explanation!).

I'm not sure of the AV-8 II differences compared to a SHAR in the respect of having water onboard available to be injected into the engine at takeoff and landing. This saves wear and tear on the engine by reducing heat and helps maintain high power settings until a heat limit is reached. So managing this extra pure water and fuel can complicate a SHAR landing but they train, practice and now how to do it (where it may seem difficult for me to explain because I have never done it). I guess I should attach the A4G/SHAR comparison PDF now in full so you get an idea. There are other 'how to land a Harrier PDFs also'.

A Harrier and an F-35B can both glide from high altitude or wherever at idle to either save/manage fuel before landing. A Harrier can quickly transition from endurance or range flying to land quickly with minimum fuel in a VL because that is what they do and practice. So the differences you perceive in your explanation above are not really there with the exception of the vertical landing at high power settings - but these are only for a short duration and in the case of the SHAR at least can be less wear and tear when using water injection.

[battleshipagincourt]

lamoey, I'm puzzling over your question: "I don't see how an airplane that has to land under full power can use less than one that sails in on close to idle trust. How do you explain that?"

How can you not understand that?

Any F-35 could glide and land conventionally if its engine were down or the aircraft ran out of fuel. If an F-35B had to land vertically, could it do a vertical landing with a dead engine?

Compared to a conventional landing, where you're throttling the engine down (and where altitude converts to airspeed), the B variant must progressively throttle UP as it lands. Possibly the argument could be made when comparing this to a carrier landing, where it can miss the cables and require another flyby.

Conventional takeoffs and landings pretty much trump all the benefits of STOVL when you've got perfectly good runways to use.

^^^

Yes I read your reply, but your explanation of 'benefits which aren't there' simply isn't true. I see that pilots can manage low-fuel landings under certain conditions, but so too can they do exactly the same with a conventional landing... and do so without requiring any fuel or even a working engine if they have enough altitude and glide speed to make the runway. The same CANNOT be done with a vertical landing under any conditions. That engine goes dead for whatever reason and the aircraft won't be landing vertically under any conditions.

[spazsinbad]

F/A-18 Hornet Barricade aboard USS Nimitz 1997 Video

http://www.youtube.com/watch?v=sD_mUwzp ... re=related

"Uploaded by wsslater on Nov 15, 2009
US Marine Hornet flown to a successful barricade arrestment aboard the USS Nimitz on or about October 24th, 1997 due to nose landing gear hung in the "up" position. Captain Scott Slater was the Marine aviator flying the jet. This was the first attempted barricade arrestment of an F/A-18 in Naval history. Captain Slater's fuel state at time of landing was excessively low. Credit for the successful landing goes to both pilot and the ship's crew for endless hours of training and execution of duties in a high pressure situation. This is incident had a pleasant ending; others do not."

More details from Mr. Slater:
“Mr.Slater (the pilot) kindly answered questions about that barricade arrestment. First, his right engine rpm's started winding down during the first pass, so what we heard was 'fluctuations on [...] right engine'. And he had 300 pounds indicated in tank 3 and all others showed 0...”
&
"My low fuel state was a result of several things. 1. Dumped fuel prior to discovering my problem in order to reduce total a/c wt. I had bombs/rockets so as ordinance goes up, fuel must go down to arrive at max gross landing weight. 2. Wingman helping me had to trap prior to stripping all wires and rigging barricade 3. Barricade was tangled, so it took some time to get it ready. Meanwhile, I'm running out of fuel."

[spazsinbad]

bsac, you bring up a good point: whether the F-35 of all persuasions will be allowed to do dead engine landings (I take your jest about an F-35B doing a dead engine vertical landing). Probably that is true given the apparent 'easy handling qualities' but what services will be available with a dead engine I don't know. These parameters will be part of the test regime I guess.

[aaam]

The Harrier can make a fully conventional landing, it's just they usually don't bother. Partly because the vertical landing doesn't really put that much excess load on the a/c, and arguably uses less fuel. Also, the Harrier is trickier to land than the F-35B will be, so just like with Navy CTOLs, practice, practice practice.

I don't see how an airplane that has to land under full power can use less than one that sails in on close to idle trust. How do you explain that?

Because the Harrier doesn't have to go through all the pattern, maneuvers and rollout plus taxi back. The period of time it is at high power is relatively small.

[aaam]

What I meant was that a Harrier lands under close to full power, while a conventional landing is more or less a glide, under the right circumstances. Some of the talk above indicates that the harrier may have to fly around until it is around 500lbs on fuel left before it can land, but in any case it would be burning a lot the last few minutes anyway. Also if a Harrier is anything like a helicopter, the ware and tear is by an order of magnitude higher during hover, so a lot of components may have much shorter survival time if hover is used a lot. A normal landing for an F-35B, on the other hand, depending on the priority and queue on final, may be a controlled glide all the way from operational altitude, without that much fuel consumption.

No, it does not have to get down to 500 lbs before it can land. The thing is that because it doesn't need to go though everything a CTOL does and isn't as concerned about waveoffs, orbiting while waiting for landing surface availability or diverts (assuming good avionics), it can afford to get down to 500 lbs without it being an immediate emergency.

A helicopter is somewhat different. For one thing, the engine (through the rotor) is providing the lift and is at high power all the time. In the Harrier, the engine only has to provide all the lift for the portion of the flight where the wing is stalled. Otherwise, it's just a regular jet. A helicopter's rotor and control system is much more complicated than that of the Harrier, and presumably the F-35B's (although the F-35B will be more complicated than the Harrier). Extended hovers are a function of airshows, not a normal operational maneuver. There are reasons beyond just fuel consumption for this.

[quicksilver]

The Harrier can make a fully conventional landing, it's just they usually don't bother. Partly because the vertical landing doesn't really put that much excess load on the a/c, and arguably uses less fuel. Also, the Harrier is trickier to land than the F-35B will be, so just like with Navy CTOLs, practice, practice practice.

I don't see how an airplane that has to land under full power can use less than one that sails in on close to idle trust. How do you explain that?

Because the Harrier doesn't have to go through all the pattern, maneuvers and rollout plus taxi back. The period of time it is at high power is relatively small.

Harrier flies essentially the same pattern as everyone else -- it just has a much wider range of options for what it does from the 180 or the FAF to touchdown. Harriers can land conventionally (ie nozzles aft) but a CL is used (intentionally) only under emergency circumstances, or when practicing landings for emergencies. Principal rolling landings are so-called 'slow landings' -- which can be fixed-nozzle/variable throttle, or variable nozzle/fixed throttle. Both options are going to use more fuel than a CL because one is using the engine to create the lift and control that the wing and aero control surfaces can no longer produce as one flies slower. Slow landings in Harrier are GW dependent but will be typically in the 100-130kt range while a CL is going to be 150+. The slower one flies, the more propulsion system lift is required.

[spazsinbad]

quicksilver, thanks for info. This version has 'auto flaps' I think to make these landings easier using fixed nozzles variable throttle technique AFAIK. The USMC Harrier AV-8B NATOPS PDF here: http://info.publicintelligence.net/AV-8B-000.pdf (36Mb)

[quicksilver]

Nice find Spaz. May still be the case today, but early-on AV-8B VNSLs used auto flaps to avoid the large flap movements that occur in STOL flaps as a consequence of excessive nozzle movement. In STOL flaps below a certain airspeed and nozzle angle, flaps program with nozzle movement -- that is not the case in auto flaps. In VNSL, pilot controls AoA with nozzle movement. Excessive nozzle movement in STOL flaps for the purpose of 'immediate' AoA control typically results in large flap reprogramming, thereby defeating the intent of the VNSL which is to preserve a finite engine performance margin for wave-off. For those unaware, all nozzle movement in the AV-8B is manual.

[spazsinbad]

Thanks for further explanation quicksilver, apparently the SHAR had better waveoff performance in this situation. It will be good to be able to have a similar level of knowledge about the F-35B one day.