All at Sea

[Weaver]

True, but then that's an emergency airfield hook for use with RAAS gear, not a carrier hook. Carrier hooks are much bigger and stronger. IIRC, I did consider a V-shaped hook that fitted around the ventral fin but it fouls the airbrakes, and if you put it behind the ventral fin (which is quite far forward) it then sits across the thrust-reverser slot, which is probably not healthy... I still think the best solution would be to fit the hook in place of the fin, forward of the thrust reverser slot and between the airbrakes, and then replace the inboard flap actuator fairings with deep, fin-shaped ones.

Now, you would'nt really need the thrust reverser on a carrier, would you?   Loose that - save a lot of weight. It will easily make up for the weight of the carrier hook (that still can be onebar style, not V-style)

Well... I started off thinking that, but consider:

1. The thrust-reverser slots also act as an ejector nozzle in normal flight, so you'd still need to either keep them or fit a petal-type nozzle, which would be a major re-build of the rear fuselage.

2. The thrust reverser lets you slow down in flight before you hit the deck, thus reducing the amount of energy the arrestor system has to absorb and the resultant stress on the airframe.

3. If you retain the land-based version's short-field capability, you retain the ability to use the carrier to deploy aircraft to minimalist land bases, which might be very useful in an intervention situation.

Sorry, didn't express myself very well there. What I mean is that the gun is a big piece of fixed payload that you can't swap for fuel/stores/recce pods on missions that don't need a gun. This isn't a problem for the air force: they can send JAs on fighter missions, AJs on strike missons and SFs on recce missions. A small carrier with maybe only a dozen aircraft in total needs them all to do every job for maximum flexibility. I'd see the carrier version having an optional gun pod for the centreline, the ability to carry Rb.71 Skyflash on the fuselage pylons and wet inboard wing pylons.

No offense taken..
The gun pod is actually rather quickly detachable as it is. It's an entirely external thing, attached to the belly of the a/c much like the belly tank on the Lightning. Leaving it off would not very likely result in more available pylon space, however, you can still not fit semirecessed AAM:s in the belly as the engine is just on the other side of the plating. Again, you could obviously use the saved weight to something more mission specific.

On the other hand, there are actually two more hardpoints already available on the inner wing, directly in line and in front of the elevon actuator aft of the main landing gear covers. These are IRL generally only used for flares and other countermeasures but in theory, you could fit lighter AAM:s there, carefully monitoring the change in CoG.

So:

• Light AAM under wing tips
• Heavy loads on main hardpoings midwing
• Light load between landing gear and elevon
• Heavier load under engine air intake
• Gun hugging centerline hardpoint
• On very short range missions - heavy loads on centerline hardpoint. Otherwise large external fuel tank

In reality, no missions were flown without that large tank as the Lightning would have seemed intercontinental in comparison..

But how much does the gunpod weigh?

I didn't mean that Skyflash on the fuselage stations would be semi-recessed: just hang it on the pylon the same as with the wing pylons.

Do you know why the main wing pylons arn't wet? It would seem an obvious way to increase flexibility......

Those inner wing pylons are interesting. Not sure what the structure's like, but it might alleviate the CofG issues if the pylon was fitted ahead of the u/c in similar fashion to the F-4 or Su-22. You could probably use the pylon as it is for bombs IF you carried the same bombs on the fuselage pylons and dropped them all at the same time. MiG-27s have to do this when using their rear fuselage pylons.

[PR19_Kit]

Can the Viggen use reverse thrust while it's airborne?

That's a pretty rare occurance IIRC. It can't be done with a Tornado, the circuit is inhibited until weight comes onto the wheels. Almost no airliners can do that, the only one I can remember is/was the DC8-63 with the 'tube engines'. Because that variant of the JT3-D engines were slow to accelerate they kept the power high and moderated the reverse in case of a go-around.

[perttime]

And how quickly can you get from reverse to full thrust?
I have understood that the normal thing during a carrier landing is to go for full thrust the instant the wheels touch the deck: it doesn't make any difference if the hook catches a cable but it gives you enough speed to fly if you miss.

A normal Gripen, at least, is programmed for full wheel and aerodynamic brakes on touchdown.

[rickshaw]

Can the Viggen use reverse thrust while it's airborne?

That's a pretty rare occurance IIRC. It can't be done with a Tornado, the circuit is inhibited until weight comes onto the wheels. Almost no airliners can do that, the only one I can remember is/was the DC8-63 with the 'tube engines'. Because that variant of the JT3-D engines were slow to accelerate they kept the power high and moderated the reverse in case of a go-around.

Might be a good way to ensure a reversion to full thrust in case of an overshoot and a go-round on a carrier approach.

I don't think the RW Viggen could do it but I don't see why it couldn't in Whiff-world.  Unlike the Tornado's thrust reversers, the Viggen's were fully contained in the fuselage.  AIUI, the Tornado's were large flags which lay on top and bottom of the fuselage, which sprang up/down and back to cover the exhaust.  They'd have caused severe attitude changes.  The Viggen's directed their thrust to the side and forward and were in the form of eyelids inside the exhaust cone of the fuselage with big slots on either side to deflect the thrust forwards.

[famvburg]

     ISTR reading that the reverser on the Viggen was tied in with a switch on the nose gear, so when the nose gear made ground contact, the reverser was activated. To use it in flight would just require some modification to the switching mechanism. However, if you're 'dragging' the (any) aircraft in just above a stall, as you would essentially on a carrier approach, you wouldn't be in a position to use reverse thrust or any other measure until you're on the deck or you'd have a stall & crash rather than a landing. With the DC-8s mentioned, my guess is their approach speeds were a fair amount above stall speed as a general rule as well as considering their engines' spool-up time. I also think I've read or heard that a number of jet aircraft with reversers use them during emergency descent such as depressurisation.

Can the Viggen use reverse thrust while it's airborne?

That's a pretty rare occurance IIRC. It can't be done with a Tornado, the circuit is inhibited until weight comes onto the wheels. Almost no airliners can do that, the only one I can remember is/was the DC8-63 with the 'tube engines'. Because that variant of the JT3-D engines were slow to accelerate they kept the power high and moderated the reverse in case of a go-around.

[PR19_Kit]

For carrier landings the FAA Buccs approached with their huge air-brakes full out and the engine thrust at a level to keep them flying OK. If they missed a wire the pilot just closed the brakes and the engines were already producing most of the poke needed for the go-around.

I'd imagine using reverse would work the same way, most reversers are pretty darn quick, even on the massive fan engines used on today's airliners, 1.5-2 secs would seem to be the time it takes to deploy them, or retract them too of course.

[Hobbes]

I'd expect a naval aircraft to be pretty close to the stall speed on approach as it is; engage the reverser a second too soon and you get a ramp strike.

[Weaver]

     ISTR reading that the reverser on the Viggen was tied in with a switch on the nose gear, so when the nose gear made ground contact, the reverser was activated. To use it in flight would just require some modification to the switching mechanism.

I thought it could be used when airborne but on further reading, I realise you're right: it was selected when airborne, but didn't engage until the nosewheel was compressed. I think I've read of it being engaged in the air at some point though: so maybe they flight-tested it at least?

For naval use, you could fit a second activation switch on the hook, so that the reverser engaged the second the aircraft caught a cable.

[McColm]

Too deep for me!!

[famvburg]

      If it caught the cable, why do you need reverse thrust?

     ISTR reading that the reverser on the Viggen was tied in with a switch on the nose gear, so when the nose gear made ground contact, the reverser was activated. To use it in flight would just require some modification to the switching mechanism.

I thought it could be used when airborne but on further reading, I realise you're right: it was selected when airborne, but didn't engage until the nosewheel was compressed. I think I've read of it being engaged in the air at some point though: so maybe they flight-tested it at least?

For naval use, you could fit a second activation switch on the hook, so that the reverser engaged the second the aircraft caught a cable.

[Weaver]

      If it caught the cable, why do you need reverse thrust?

Reduce the stress on the airframe, shorten the landing run still further and reduce the size of the arrestor gear. Remember, these are SMALL carriers that we're talking about.

[Old Wombat]

Carrier approaches are generally carried out with everything hanging out to increase drag so that the engines can be held at the highest power possible until the hook grabs & the approach is controlled via the throttles. This is done so that there is sufficient power available to the pilot so that he can ram the throttles wide open without worrying about wind-up lag or the fear of flooding the engine(s) & loosing power instead of increasing it, & he just has to slam shut the air-brakes & flaps to reduce drag so he gains airspeed faster.

Now, if you attached a thrust-reverse actuator switch to the hook, then you could apply full power earlier, as the wheels hit the deck for example, so that if you don't hook the wires you can close the brakes & raise the flaps earlier & go around much more safely but, if you catch the hook, the reverse thrust kicks in at full power cutting speed & reducing stress on the airframe.

However, for that to work effectively, you need full reverse thrust to be activated in under 0.1 seconds - otherwise it's too late to do any good.

..... & it's another system to maintain, which can fail when you need it most.

[Pellson]

1. The thrust-reverser slots also act as an ejector nozzle in normal flight, so you'd still need to either keep them or fit a petal-type nozzle, which would be a major re-build of the rear fuselage.

No, the slots are entirely closed by the reverser eyelids when in flight.

2. The thrust reverser lets you slow down in flight before you hit the deck, thus reducing the amount of energy the arrestor system has to absorb and the resultant stress on the airframe.

Tricky. Generally, the Viggen used the angle of attack to be able to fly finals with low speed and almost full thrust. This can be viewed in several Youtube episodes. Using the reverser seems thus just complicated and unneccesary. IRL, the spool-up from the level of thrust applied at finals were short enought to actually get the a/c airborne again within 50 meters after touchdown, should that be required.
However, if we're whiffing...

3. If you retain the land-based version's short-field capability, you retain the ability to use the carrier to deploy aircraft to minimalist land bases, which might be very useful in an intervention situation.

Indeed. It should however be noted that the Viggen's successor, the SAAB 39 Gripen, uses aerodynamically braking by angling the canards aggressively in combination with a brake chute. Obviously, a chute would easily fit within an extended fairing either above of below the exhaust also on the Viggen.

But how much does the gunpod weigh?

I didn't mean that Skyflash on the fuselage stations would be semi-recessed: just hang it on the pylon the same as with the wing pylons.

The gun weight is 136 kg empty. Add for some rounds..
Note that the round used in the Viggen gun is the same round used by the A-10 GAU-8 gun. Quite powerful thingys..

Do you know why the main wing pylons aren't wet? It would seem an obvious way to increase flexibility......

These aircraft were specifically designed for the defence of Sweden, and the use of a distributed network of road bases really did mean that any extended range was unnecessary as there always was a field more or less in sight.

Those inner wing pylons are interesting. Not sure what the structure's like, but it might alleviate the CofG issues if the pylon was fitted ahead of the u/c in similar fashion to the F-4 or Su-22. You could probably use the pylon as it is for bombs IF you carried the same bombs on the fuselage pylons and dropped them all at the same time. MiG-27s have to do this when using their rear fuselage pylons.

IRL, that option didn't exist. However, this isn't IRL.. 

[The Rat]

Carrier approaches are generally carried out with everything hanging out to increase drag so that the engines can be held at the highest power possible until the hook grabs & the approach is controlled via the throttles. This is done so that there is sufficient power available to the pilot so that he can ram the throttles wide open without worrying about wind-up lag or the fear of flooding the engine(s) & loosing power instead of increasing it, & he just has to slam shut the air-brakes & flaps to reduce drag so he gains airspeed faster.

Now, if you attached a thrust-reverse actuator switch to the hook, then you could apply full power earlier, as the wheels hit the deck for example, so that if you don't hook the wires you can close the brakes & raise the flaps earlier & go around much more safely but, if you catch the hook, the reverse thrust kicks in at full power cutting speed & reducing stress on the airframe.

However, for that to work effectively, you need full reverse thrust to be activated in under 0.1 seconds - otherwise it's too late to do any good.

..... & it's another system to maintain, which can fail when you need it most.

Harriers are starting to look pretty good right now, eh?   

[Old Wombat]

I always thought they did ..... but they do have a limited payload compared to (most) cat-launched aircraft .