BAe/Boeing GR.5 / AV-8B wings-span 'What If' question????

[PR19_Kit]

So would the Harrier land gear down and then maneuver into the cradle, or land directly into the cradle?

Weaver's post  #52 answered that I think, with his cable actuated cradles that centered the aircraft after it landed anywhere it managed to on the platform.

I proposed a more complex solution which used hoverpads and hydraulics but Weaver's cable method is much simpler and lighter.

[Weaver]

Autoland? AUTOLAND!!!! I can hear Sir Sydney Camm contra-rotating in his grave! He was dead set against any form of autopilot or autostabiliser on the Harrier, insisting on getting the control system right, rather than fixing it with electronics. This was a major reason why the Harrier was cheaper and simpler than much of the V/STOL opposition.

Of course, he was dealing with 1950s/60s electronics, which were heavy and unreliable, whereas modern ones are different tray of chips altogther.

[coops213]

Well I guess it depends when this what-if is set. But if a bunch of students can do this with a few hundred bucks an a PC, retrofitting the Harrier with an autonomous landing system would be fairly trivial for Boeing engineers. The AV-8BII+ was fly by wire anyway, wasn't it?

Chris

[Weaver]

Well I guess it depends when this what-if is set. But if a bunch of students can do this with a few hundred bucks an a PC, retrofitting the Harrier with an autonomous landing system would be fairly trivial for Boeing engineers. The AV-8BII+ was fly by wire anyway, wasn't it?

Chris

Oh sure, I was being old-fashioned - you can make a brick dance swan lake in mid-air with enough thrust and a PC these days. However, I'd like to see how precisely that quadrotor could be controlled if it weighed a couple of tons and had to land in a gusting cross-wind. I'm sure it'd get down, but I wouldn't put money on it being so precise that you wouldn't have to move it afterwards in order to pack it up in a rail car.

I don't think the AV-8BII+ is fly-by-wire as such, but it does have some extra help - auto throttle maybe?

[PR19_Kit]

Well I guess it depends when this what-if is set. But if a bunch of students can do this with a few hundred bucks an a PC, retrofitting the Harrier with an autonomous landing system would be fairly trivial for Boeing engineers. The AV-8BII+ was fly by wire anyway, wasn't it?

AFAIK even the latest Harrier models have the 'cross wind yaw' issues, and no amount of electronics would seem to overcome the 'Mk 1 Eyeball' being able to sort that out. One solution would be to make the wings straight, like at 90 deg to fuselage, but that would tend to defeat one of the objects of the exercise.....

[coops213]

Oh sure, I was being old-fashioned - you can make a brick dance swan lake in mid-air with enough thrust and a PC these days. However, I'd like to see how precisely that quadrotor could be controlled if it weighed a couple of tons and had to land in a gusting cross-wind. I'm sure it'd get down, but I wouldn't put money on it being so precise that you wouldn't have to move it afterwards in order to pack it up in a rail car.

I don't think the AV-8BII+ is fly-by-wire as such, but it does have some extra help - auto throttle maybe?

With the right kind of systems in place I don't think it would be any harder to achieve than, say, plugging a fuel receptacle into the end of a basket towed by another aircraft while in flight. However, if the AV-8B isn't fly by wire it would probably be far to complicated to try and implement such a system. Maybe this calls for an all-digital AV-8C, complete with flight computer!

PR19_Kit, I'm not familiar with the cross wind yaw issue, what did it involve?

Chris

[PR19_Kit]

PR19_Kit, I'm not familiar with the cross wind yaw issue, what did it involve?

When flying at low or zero airspeeds, usually while making a vertical landing, the Harrier has to point exactly into the apparent wind. If not, the wing that's not so swept, compared to the apparent wind, generates more lift than the other one and the aircraft rolls toward the non-lifting wing. Numerous accidents occured during the initial flights by the RAF's 233 OCU and No. 1 Sqdn., and also during the early flights carried out by the USMC.

Great care has to be exercised by the pilot to keep the aircraft pointed directly into the apparent wind, and this is the reason for the sailplane type wind vane directly in front of the windscreen. As far as I can see even the later GR9s have them. The AV8B+ may also, but I can't find a close-up view of the nose yet. In any case the problem still exists for any type of swept wing VSTOL aircraft.

[Hobbes]

I know that logistic was a big issue but i had no idea it was this big of a issue. This is what I found out while trying to get more information of the types of airfield equipment.

from http://www.globalsecurity.org/military/library/policy/army/fm/5-430-00-2/Ch11.htm if sq ft can be converted in to ISO containers that is a 100 to nearly 200 boxes need for what I seems to be a two week operating period. Fuel seems to be as bad though all I found was a suggestion of 15000 bbl for some undefined type of military airbase.

How sneaky is a 200 car train?

Keep in mind though that that table is from a guide on building full-blown airfields. For instance see the column on 'small-arms ammo' which isn't going to be for the aircraft, but for base personnel. For a forward base with a couple of Harriers, the requirements are going to be way off. Still, a couple of tons of ammo+fuel per flight adds up quickly.

[kitnut617]

Also, you can bring up more on another train, like the ships do --- that is if the line hasn't been sabotaged by the local partisans   

[Weaver]

Oh sure, I was being old-fashioned - you can make a brick dance swan lake in mid-air with enough thrust and a PC these days. However, I'd like to see how precisely that quadrotor could be controlled if it weighed a couple of tons and had to land in a gusting cross-wind. I'm sure it'd get down, but I wouldn't put money on it being so precise that you wouldn't have to move it afterwards in order to pack it up in a rail car.

I don't think the AV-8BII+ is fly-by-wire as such, but it does have some extra help - auto throttle maybe?

With the right kind of systems in place I don't think it would be any harder to achieve than, say, plugging a fuel receptacle into the end of a basket towed by another aircraft while in flight. However, if the AV-8B isn't fly by wire it would probably be far to complicated to try and implement such a system. Maybe this calls for an all-digital AV-8C, complete with flight computer!

PR19_Kit, I'm not familiar with the cross wind yaw issue, what did it involve?

Chris

I have to respectfully disagree: I think it's the equivalent of plugging a fuel receptacle into the end of a basket and then reeling in the reciever until it docks with the tanker. My point about mass is that it governs inertia, which in turn governs the response speed possible with a reaction control system of a given power. If the Harrier is descending and a gust catches it at the last second, it's likely to have hit the ground off-centre before your autopilot can detect the gust, apply the reaction control jets and get a result. Of course, you can make the RCS more powerful, but that still doesn't get over the sense-decide-react loop delay, and of course, it means bleeding more air from the engine.

Wasn't there a Harrier test aircraft with FBW used to develop systems for the JSF?

[PR19_Kit]

Wasn't there a Harrier test aircraft with FBW used to develop systems for the JSF?

Yes, it was a 2 seater based at Boscombe Down and has almost a complete chapter devoted to its work on John Farley's book, 'A View from the Hover'. It had a standard Harrier control system in one cockpit (the rear I think, but could be wrong) and the various FBW systems wired into the front cockpit. The monitoring pilot in the standard cockpit could take-over instantaneously if anything went wrong, and the system itself could switch back to standard mode if it detected a failure.

They developed the very sophisticated control mode used in the F-35, which is totally different to that used in a Harrier, using this aircraft. If I could find the darn book I'd quote chapter and verse ad nausiam! 

That's where I got a lot of the info on the yaw problem from too, John Farley writes a very good, absorobing and simple to understand book, even about something as complex as VSTOL.

[MAD]

coops213 -Maybe this calls for an all-digital AV-8C, complete with flight computer!

Although this might mean you would have to term it the AV-8E & TAV-8E, for as from 1979 the USMC started upgrading their AV-8A Harriers to the AV-8C!

I am love and learning lots from the 'for and against' discussion gents!
But lets not get to bogged down in actual micro details, as we are looking at 'what if'

I am still hoping that this discussion might lead to some actual profiles 

M.A.D

[rickshaw]

Let me put forward a proposal.

Each Harrier would be assigned three road trains.   Two for operations and one for logistics.  The two operational ones would be provided with the following:

Steel matting sufficient to build a landing pad
Accommodation for ground and air crew
Sufficient POL tankerage for 24 hours flying.
Sufficient Ammunition for 24 hours flying.
MANPADS air defence.
A platoon of infantry for local defence (travelling in separate vehicles).

The logistics road train would carry sufficient fuel and ammunition for 48 hours operation.

Road trains would operate semi-independently, with the Harriers flying between them and being called up to mount strikes in concert.

The aircraft would operate from PSP steel mat landing pads.   The road trains would be able, because of the large network of bush tracks and roads to range in and around an operational area and be able to provide rapid and timely air support to troops engaged with the enemy.

I would foresee that on the march, the Harrier road train would be something like:

Scout Vehicle  (Landrover equipped with HMG & LMG)
Troop Vehicles  (Landrover troop carriers)
Road Train vehicle  (B-Couple semi-trailer equipped with multiple wheel drive)
MANPADS Vehicle  (Landrover carrying MANPADS team(s) ).
Troop Vehicles
Scout Vehicle

Logistic road trains would consist of:

Scout Vehicle
Road Train vehicle
Scout Vehicle

This way, a landing pad could be erected at short notice, aircraft could land, as required "into the wind" and FOD would be kept to a minimum and be quickly refuelled and rearmed, ready for their next sortie.   While one operational road train is in use as a FOB, the other could be moving to a new location and setting up.  Therefore complicating the targeting of FOBs by the enemy.

The Logistics road train would be pushed forward to which ever FOB required resupply on an "at need" basis, returning to a FLB (Forward Logistics Base) for resupply itself.

[Hobbes]

Road trains work well on flat, paved roads. Over hills or off-road you'd soon struggle with insufficient power and/or traction to pull the train. You'd have to add powered axles to every trailer, and then you need a huge prime mover to generate enough electric power for those trailers.
You may be better off using trucks that are already in the Army's inventory: container/pallet-loading trucks for supplies, and something like a tank transporter for the landing pad. This also adds flexibility to your operation.

[rickshaw]

Road trains work well on flat, paved roads. Over hills or off-road you'd soon struggle with insufficient power and/or traction to pull the train. You'd have to add powered axles to every trailer, and then you need a huge prime mover to generate enough electric power for those trailers.

Assuming of course you're going to go for electric power for the trailers.  The Russians utilised power takeoff systems for theirs and they seem to work quite well.   As I suggested they actually be used on-road, rather than off-road, I think the point is a little moot.  You're also assuming that they would be fully loaded to capacity whereas I rather think what they are carrying is less than that.

You may be better off using trucks that are already in the Army's inventory: container/pallet-loading trucks for supplies, and something like a tank transporter for the landing pad. This also adds flexibility to your operation.

I'm trying to avoid the idea of actually trying to land on and take off from the truck.  I see little value in it when you can have a steel PSP mat landing pad which can be knocked down and put up in less than 15 minutes.  With a couple of self-loading cranes, you could be set up or gone in less than 60 minutes - which is usually more than sufficient for most operations.