Design Challenge: Loyal Wingman / Advanced Trainer / Light Combat Aircraft

[H_K]

Starting a discussion on Loyal Wingmen and whether the same platform could be derived into piloted aircraft for advanced training or light combat missions.

- We know that the USAF wants larger, higher performance Loyal Wingmen (vs. the MQ-28 Ghost Bat or XQ-58 Valkyrie). Presumably this means transonic performance (minimum Mach 0.8-0.9), and ideally supersonic performance (Mach 1.2-1.4?) for air-to-air, penetration & interdiction missions, with good survivability and sufficient internal weapons (2x AAMs or 4x 125kg class SDBs or equivalent?). Other air forces are likely to follow the same path in order to complement their expensive 6th generation fighters.

- The USAF are willing to pay 1/3rd the cost of an F-35, i.e. $20M+... much more than the <$10M being advertised for Valkyrie and other simpler/slower/smaller platforms... so this is no longer meant to be an attritable aircraft, though high loss rates will be acceptable.

- All-in-all, this means that these Loyal Wingmen will start to overlap with manned jet aircraft, especially advanced trainers / light combat aircraft like the T-50/FA-50, in terms of performance / cost / non-attritability etc. Can one platform cover both roles?

 

[kqcke for you]

Starting a discussion on Loyal Wingmen and whether the same platform could be derived into piloted aircraft for advanced training or light combat missions.

- We know that the USAF wants larger, higher performance Loyal Wingmen (vs. the MQ-28 Ghost Bat or XQ-58 Valkyrie). Presumably this means transonic performance (minimum Mach 0.8-0.9), and ideally supersonic performance (Mach 1.2-1.4?) for air-to-air, penetration & interdiction missions, with good survivability and sufficient internal weapons (2x AAMs or 4x 125kg class SDBs or equivalent?). Other air forces are likely to follow the same path in order to complement their expensive 6th generation fighters.

- The USAF are willing to pay 1/3rd the cost of an F-35, i.e. $20M+... much more than the <$10M being advertised for Valkyrie and other simpler/slower/smaller platforms... so this is no longer meant to be an attritable aircraft, though high loss rates will be accetable.

- All-in-all, this means that these Loyal Wingmen will start to overlap with manned jet aircraft, especially advanced trainers / light combat aircraft like the T-50/FA-50, in terms of performance / cost / non-attritability etc. Can one platform cover both roles?

Should be tought having an optional unmanned jet makes probaly a lot of dead weight for the UCAV. But as the newest scaled composite Model 437 shows its likely possible/ will become possible.

 

[H_K]

To illustrate my thought process, I went back to some of the earliest small transonic fighter designs from the 1950s. These include Dassault's Mirage I/II and Etendard VI (one could pick other equivalent designs from other manufacturers, but these 2 are well documented).

What I like about these designs as a conceptual starting point is their small size, low weight (<4 tons empty), low drag, and thus their ability to fly transonically despite weak engines (5,000 - 8,000 lbf thrust). We know that today the most obvious weaknesses of these smaller 1950s fighter designs could be compensated with advanced flight controls, more powerful and fuel efficient engines, and RCS reduction measures.

So I'm postulating that one could start with the same dimensions as a 1950s Mirage II or Etendard VI and start with 2 key changes to obtain a fairly high performance 4t empty aircraft:
1) A modern engine, likely in the 9,000 - 12,000lb thrust range (either F125, Adour or AI-322F with afterburning, or dry F404/M88/EJ200 without afterburning)
2) An advanced wing, e.g. delta+Levcons, delta+canard, or YF-23-like with pelican tail

Then one would start layering in RCS reduction measures (shaping + internal weapons bay). I believe the minimum internal weapons bay would have to measure roughly 3.8m x 0.7m x 0.4m (L/W/H) or about 1,000 liters in order to fit 2x AAMs or 4x 125kg class bombs (e.g. SDB I/II, Spear 3, Spice 250ER, Smart Glider etc) or alternatively 2x 250kg class bombs - this is in fact what Airbus has shown in some of their concepts. This weapons bay would likely be impossible to accommodate on the piloted aircraft (due to the aircraft's small size), but could fit on the Loyal Wingman ahead of the engine/landing gear if the equivalent volume in fuel was moved from belly tanks to the cockpit area.

To illustrate, here is a small platform with triple delta wing + Levcons showing similar dimensions to the 1950s Mirage II and Etendard VI. Also including a size comparison to the larger Mirage 2000 and M-346 advanced trainer to show the diminutive size.

Next up... discussion of internal arrangements... how to fit engine, fuel, landing gear and weapons bay into such a tight package!

 

[red admiral]

- All-in-all, this means that these Loyal Wingmen will start to overlap with manned jet aircraft, especially advanced trainers / light combat aircraft like the T-50/FA-50, in terms of performance / cost / non-attritability etc. Can one platform cover both roles?

Yes from a technical / operstional perspective. Plenty of other historical examples too e.g. AMX, Saab B3LA etc. Internal carriage drives quite a large fuselage with volume that could be used for a cockpit.

I think the main challenge for the CCA side though is keeping the cost down by avoidance of any unnecessary creep; e.g. crewed aircraft can bring extra airworthiness requirements such as moving to multiplex electrical/hydraulic control systems. So I'm not convinced that its a "good" idea. CCAs should be low cost to get the numbers.

I believe the minimum internal weapons bay would have to measure roughly 3.8m x 0.7m x 0.4m (L/W/H)

Those dimensions start to increase quite a bit once you add the likes of launchers, hinges, latches, actuators, spoilers for flow control etc. Which flows through into quite a big impact on the fuselage size, drag, mass etc.

 

[H_K]

And here's the start of an internal arrangement sketch. I'm working off an F404 engine without afterburning and the X-29's fuselage/inlet layout in order to ensure proper area ruling. Sadly I don't have the ability to model this in 3D or to draw cross-sections in order to measure volumes to determine how much would be available for fuel*, accessories, weapons bay etc... mostly just going off existing design arrangements and extrapolating from there.

@red admiral do you have an estimate of weapon bay dimensions to accommodate 2 AAMs or 4x SDBs? I'm basing my dimensions on the Silent Hornet External Weapons Pod.

*Fuel calcs: minimum requirement for 400-550nm combat radius hi-hi-hi would be 1,800kg fuel, with as much as possible in the wing - estimate based on ~4t empty weight and 6-6.5t take off weight, with fuel flow scaled down from an F/A-18C with F404 engine.

 

[The K2]

The way UCAVs are getting bigger and more sophisticated, I wondered about the same thing: can one platform carry two roles. Saw this concept from Airbus and thought about it: https://www.twz.com/air/the-airbus-wingman-stealth-drone-what-we-learned-in-berlin

 

[red admiral]

@red admiral do you have an estimate of weapon bay dimensions to accommodate 2 AAMs or 4x SDBs? I'm basing my dimensions on the Silent Hornet External Weapons Pod.

I think you need extra height as a minimum to accommodate door (non zero thickness) + gap + weapon + launcher + room for hand access, which easily gives ~0.6-0.7m height I think. Maybe you can save a bit by havjng the SDBs on individual launchers rather than the quad pack. Length probably a bit longer unless you have a trapeze arrangement to move the AAMs out of the bay first whilst restraining movement.

I'd note that anything bigger than AMRAAM e.g. Meteor, will need more space

 

[VTOLicious]

I think you need extra height as a minimum to accommodate door (non zero thickness) + gap + weapon + launcher + room for hand access, which easily gives ~0.6-0.7m height I think. Maybe you can save a bit by havjng the SDBs on individual launchers rather than the quad pack. Length probably a bit longer unless you have a trapeze arrangement to move the AAMs out of the bay first whilst restraining movement.

I'd note that anything bigger than AMRAAM e.g. Meteor, will need more space

Have a look here...
https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-506704
...That's the minimum space required for 4x AMRAAM. The design is based on the layout of Boeing's Enclosed Weapons Pod.

 

[red admiral]

...That's the minimum space required for 4x AMRAAM. The design is based on the layout of Boeing's Enclosed Weapons Pod.

So fir 2 AMRAAMs then you could reduce the height a bit (250-300mm?), but then you can't fit in 4 x SDBs without going to individual launchers instead of the existing quad pack.

From a fuselage integration side, then almost this whole bay has to protrude out of the bottom of the fuselage in order for the doors to open. And the sides are vertical. A more sympathetic integration (e.g. canted fuselage sides) will increase the width and volume required.

 

[Basil]

... already mentioned in another thread, but if you can do without an internal missile carriage, this Swiss concept is a good starting point:

https://www.alr-aerospace.ch/publications/Bridel,%20G%20Janus%20Concept,%20SMi%20Conference,%20London%20September%202016.pdf

 

[Scott Kenny]

... already mentioned in another thread, but if you can do without an internal missile carriage, this Swiss concept is a good starting point:

https://www.alr-aerospace.ch/publications/Bridel,%20G%20Janus%20Concept,%20SMi%20Conference,%20London%20September%202016.pdf

How are you proposing to have a stealthy airframe without internal weapons?

 

[Basil]

How are you proposing to have a stealthy airframe without internal weapons?

It would not be stealthy like an F-35 but its small size has advantages in visibility.

 

[Scott Kenny]

It would not be stealthy like an F-35 but its small size has advantages in visibility.

I don't care if I can barely see it visually if I can see it from 200km away on radar.