Launching and Landing a plane from a blimp?

One consequence of any ATL where Zeppelins survive is the idea of launching small aircraft from "Air-Aircraft carriers". Has this ever been done in OTL?
 

Thande

Donor
They were referred to as "parasite aircraft", by analogy to those parasitic fish that stick themselves on the side of a shark or whale.
 
See:

http://en.wikipedia.org/wiki/Parasite_aircraft

http://en.wikipedia.org/wiki/McDonnell_XF-85_Goblin

for examples.

In general parasite aircraft have not been adopted because they:

1) Reduce the capability of the parent aircraft too much. The weight of the aircraft plus the gear for launch and recovery considerably reduces the payload of the aircraft and/or its fuel load, which reduces its range.

2) Have too small a radius of action to adequately protect the parent aircraft. To be carried it has to be light, therefore cannot carry much fuel, therefore short ranged. Light also means reduced armament, which means less effective.

3) Are too difficult to launch and recover from the parent aircraft compared to conventional aircraft. Recovering an intact parasite aircraft under ideal conditions is difficult enough; recovering a damaged one under combat conditions would be well nigh impossible.
 
Blimps

Actually, aircraft have only been launched and recovered from rigid airsips. Blimps are too small and not strong enough to handle aircraft, as far as I know.
 
Launching aircraft is possible from any lighter-than-air vehicle large enough to carry it, including balloons. Recovery is only possible where speeds are compatible. In theory, you should be able to recover a Harrier onto a balloon.
 
Something like this.

8-12_indoor_blimps.gif
 
Actually, aircraft have only been launched and recovered from rigid airsips. Blimps are too small and not strong enough to handle aircraft, as far as I know.

They are much smaller than the big rigids were, which is a liability--as for "strong" that depends--a modern blimp certainly can be quite as strong in proportion to its total load as the best of the old rigids was, and possibly has to be stronger.

For instance, the reason airships shouldn't be made to go too fast is structural; the bending moment on the structure is proportional to the volume--and the square of the airspeed. Yet, the fastest airspeed I know of that an airship ever attained was done by a blimp--I believe, IIRC, a US Navy ZPG ship in the late 50s, which went over 80 knots. (I've been told this is an unofficial record, and that the crew did it by redlining everything--not just engines but envelope pressure!) But this beats the top speeds of such rigids as the Macon and the Hindenburg. So actually while for many missions, such as advertising, there is no need to make the ship strong or powerful and thus economies of weight can be realized in lightening a ship to milder specifications, certainly even a pressure ship can be made strong enough.

As witness:

During WWII Goodyear Aircraft Corporation developed the "M" class blimps, of originally 625,000 cubic feet, later expanded to 725,000 cf. That's 16875 cubic meters versus 19575. There were eventually bigger blimps, the ZPG class radar ships of the late 50s, but for quite some time these were the biggest non-rigids. The first one, redesignated XM-1 when it got a 675,000 cf envelope (a bit over 18,000 m^3), max speed 69 knots, was used to try some hook on operations.

James Shock:US Navy Airships; Atlantis Proudctions 2001 Edgewater FL p. 155 said:
XM-1 was flown with an NE-1 Piper Cub airplane on radio control and guidance experiments in early 1944. Several flights were made in March and April 1944 with the Piper Cub ("Glimpy") supported from the forward car section...On 13 March the manned Glimpy was released for return flight at an altitude of approximately 1000 feet. Glimpy flew again on 17 April and 27 April 1944.

Well, that doesn't settle whether Glimpy was able to hook on in flight or not, but now I am reminded, long before this, indeed before the US Navy began hook-on trials on the USS Los Angeles, the US Army had already demonstrated hook-ons with a much smaller blimp in the 1920s:

Here we go, from Shock's companion Army airships volume, the characteristics of the TC-5 on p. 104--volume 200,600 cf, around 5400 m^3; total lift with helium 11,584 pounds; useful lift 3700 pounds, maximum speed 52 mph.

James Shock:US Army Airships; Atlantis Proudctions 2002 Edgewater FL p. 101 said:
During the period of October 2-4, 1924 the TC-5 successfully launched a Sperry Messenger airplane over Wilbur Wright Field, Dayto, Ohio...the trapeze bar...extended about 9 feet below the control car...For airplane test flights, the airship was weighed off 1,200 pounds statically "light" (about the weight of the plane)...It headed into the wind with the engines at full throttle until the the airship reached an altitude of 1,500 feet...The crew was not aware of the successful release until the airplane was approximately 100 feet below the airship. No difficulties were experienced with either airship or airplane, and Lt. Finter reported he could move the airplane left or right on the trapeze and he could use his elevators to elevate or depress the nose of the airplane. These experiments convinced the Army it would be much easier to attach the airplane in the air than on the ground...

Shock said:
On December 15, 1924, the TC-3, piloted by Lt. Frank McKee, was used successfully for first trapeze hook-on of an airplane. Lt. Clyde V. Finter piloted the Sperry Messenger airplane and the hook-on was made 1500 feet above Scott Field.

The TC-3, though from an older series of the Army C class, had the same volume, gross lift, and top speed of 52 MPH as the TC-5.

So there--the very first hook-on ever was on a blimp!:p

Now to be sure, these Messengers and Piper Cubs were very light planes with very low stalling speeds (obviously, if 52 mph sufficed!) For that matter, the Navy's Curtiss Sparrowhawk biplane fighter/scouts of a decade later, though deemed competitive in performance in their early 1930s era, had top speeds not much over 200 knots, and were among the lightest and smallest linear-dimensioned planes ever adopted for fighter service by any air arm of any country in any period (even WWI light fighters were all heavier!)

The key to easy hook-ons was of course that the plane's stalling speed was below the airspeed the airship was keeping. Since airships of any size can't be made to go a lot faster than the 60-70 knot maximums reached by the big rigids of the late 20s and early 30s, it might seem the idea of hook-on planes is DOA.

However, I do believe that planes can manage to engage a trapeze that is suspended a considerable distance below an airship in a flyby, and then swing on that to kill its excess speed by gravity; at the top of the swing a secondary line can engage to hold it there and reel the arrangement in. Doing so would first require considerable pilot skill, second lines and a suspension arrangement that can take the sudden shock of twice the plane's weight (centrifugal force would double it at the bottom of the swing though of course it falls to zero at the top!).

But the pilots in the USN's hook-on program (who operated off of three rigids, the Los Angeles, the Akron, and Macon) reported that their landings (onto a fixed trapeze at the same speed as the rigid, to be sure) were a lot easier than landing on the deck of a seaborne conventional carrier. For one thing, they were flying in the same wind as their carrier, so any changes in the wind applied to both aircraft simultaneously, leaving the pilots to have to worry only about turbulence, which was partially a matter of making the trapeze long enough. For another, coming up to their mother ship from below instead of descending on it from above, gravity to an extent became their friend rather than enemy; in case of a botched engagement they were unlikely to collide with the airship, and they had plenty of clearance below to dive down for airspeed and go around if that proved necessary.

Even if a dynamic engagement of a trapeze hanging some distance below the airship at a high relative speed of as much as 100 knots were necessary, both these advantages would still be present. If a 160 knot airspeed in final approach is necessary (as it might be for some very "hot" jet planes) then obviously a surface carrier landing is even more fraught with hazard and uncertainty, as a surface carrier capable of no more than 30 knots sea speed would have to be steaming straight into a 30 knot wind to match the airspeed of a cruising airship, and it would still be subject to waves that rock the deck, the wind could easily shift much faster than the ship could steer into it, and the plane is still coming in at 100 knots relative to the deck! If a Navy pilot can manage to snare a wire on that deck with a tailhook and survive being jerked to a halt from 50 meters/sec to zero, surely that same pilot can, at least with the sort of radio or laser assisted homing guidance that would have been becoming available around the same time as suitable jet engines for such a plane, snag a hook deployed behind him onto a trapeze above him. If it works the mere 2 G pull on him and his plane is nothing compared to a routine carrier landing; if it doesn't he is much less likely to wreck himself right there, has plenty of speed and height for a go-around, and is far less likely to do any damage to his carrier. A trapeze that can reduce a 50 meter/sec relative speed to zero by gravity swing alone would be about 250 meters long! But an airship capable of handling squadrons of modern fighter jets, whose most petite versions mass upward of 10 tons (the Navy F-14 came closer to 40 tons!) will be a lot longer than Macon's 235 meters long anyway! Besides I do believe the trapezes might be shorter considering that the pilot can also slow the plane down a lot by aerobraking means once securely hooked, but frankly I have trouble analyzing that and so stick with simple frictionless gravity swing concepts.

So--back to blimps. Of course first of all you need enough gas volume to lift the airplane in question; that isn't really a matter of the total lift, but the useful lift left over after subtracting basic structure weight, crew, fuel, etc. Even the TC-3, which landed a plane for the first time, and a very light plane at that, did not then swing the plane up to the control car and take the pilot on board, let alone refuel the plane etc. To do that extra stuff we need a bit more than a trapeze, we need to winch up the plane at the very least. So, the bigger the plane and more elaborate what we want to do with the plane is, the more useful lift we need, for the plane itself, for a fancier landing system, for refuel, rearming loads, alternate pilots, etc. Not to mention machine equipment and spares for maintenance!

If all you want to do, as with the Naval M ships of WWII, is extend scouting range and perhaps by some stealth by having the actual eyeball first contact be made by a small light plane the enemy might be less likely to see in the sky than a big blimp, then you really don't need a whole lot of airplane; something like a Piper Cub, stripped down further in fact, will do just fine; two of them would be enough to greatly widen the range of the blimp's effective surveillance. (For one thing, they can fly higher pretty easily, whereas a blimp has to trade off lift to gain a higher ceiling. So even one plane can greatly widen the track searched, by climbing higher). Such an airplane can easily have a stall speed well under 60 knots.

If on the other hand it is your goal to harbor a squadron of modern fighter/bomber jets, you clearly have a more demanding task in front of you! Just to lift the planes the size of the ship must be much greater; to carry the extra margin of ammo, fuel, relief pilots etc requires more...The total weight of the 5 Sparrowhawk fighters carried by Macon, all gassed and bombed up, was 6 tons altogether. Clearly something that can match the capabilities of a supercarrier like the USS Nimitz will probably wind up massing as much! At 100,000 tons I figure an airship carrier of that mass would be something like a nautical mile long!:eek::cool: I do think that one could manage a very small strike force with no reloads with something much more reasonable in size, but it would still be a big ship compared to any "blimp."

But it's not carved in stone that such a big ship can't be a blimp, just a very big one!
 
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Theoretically one can develop a flight deck on top of a zeppelin with the weight hooked onto the bottom. You can use that in all kinds of recover/launch airplane solutions, bonus points if you have a hook or throw them off the side launch/recovery solution as well.
 
Theoretically one can develop a flight deck on top of a zeppelin with the weight hooked onto the bottom. You can use that in all kinds of recover/launch airplane solutions, bonus points if you have a hook or throw them off the side launch/recovery solution as well.

And helicopters would be better than conventional aircraft because stall speed is no longer a consideration and the landing area need not be much bigger than the rotor diameter. There would also need to be internal storage for the helicopters when not in operation to protect them from lightning, hail, and icing.
 
Theoretically one can develop a flight deck on top of a zeppelin with the weight hooked onto the bottom. You can use that in all kinds of recover/launch airplane solutions, bonus points if you have a hook or throw them off the side launch/recovery solution as well.

I'm not sure what you mean by "with the weight hooked on the bottom" here!

Yes, instead of requiring planes to have a hook mounted to their center of mass on top, one could put a runway for conventional wheeled planes to land on top. It's a little bit better than a seaborne conventional carrier deck, but there are all sorts of drawbacks compared to hooking on from below:

1) weight distribution of the system in the airship--a hanging system puts all the weight on the bottom of the airship, where it helps with pendulum stability--putting stuff up on top puts the overall center of mass of the ship higher and potentially above the center of lift, which makes the ship unstable, likely to roll. (For related reasons, dropping and recovering craft from the "sides" is a bad idea because either you need to synchronize drops and pick-ups on port and starboard, or the ship gets the worst roll moment that weight change could possibly impart!)
1a) efficiency of suspension--designing a means of supporting a rigid runway up on top, not to mention the greater all up weight of a distributed runway versus a single trapeze, even one on a long pendulum line, is surely going to involve more overall weight than suspending a hook-on system, however elaborate, below.

2) the operational advantage a hook-on plane enjoys, of being aided by gravity rather than having to outmaneuver it with failure meaning disaster for both plane and carrier, is tossed aside for a flight deck on the back; landing on back is just like landing on a surface carrier in this respect! Except that a "ramp strike" or overshoot while failing to gain enough airspeed to clear the ship and go around would not merely result in local damage to the flight deck or losing plane and pilot in the drink (or both getting ground under the keel and chopped up by the props)--no, here it's all too likely the plane plummets right through the aerostatic hull, ripping up the gas containment and perhaps falling to the ground or water below after doing so anyway.

It's what one would need to handle an airplane not equipped with any kind of hook system obviously.

Now on the other hand, for helicopters, obviously they'd need to land on the back somewhere; it's pretty hard to imagine a workable hook system for them--it would have to come up from the hub, or between the rotors of two-rotor designs (which aren't so popular lately). Either way the pilot has a hard time seeing it clearly and then the rotors have to be shut down for anything to transfer between ship and helicopter. But a heliport on the back seems much less problematic than a runway there!

Still, it isn't really better than a heliport on any surface ship. It just doesn't excite me as much as the notion of being able to launch and land airplanes, which distinguishes an airship from most surface ships, with only the exception of a big expensive deck carrier.
 

Cook

Banned
Recovering or Docking rather than Landing would seem to make more sense by the way.
 
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