|QUOTE (Lamoni @ May 25 2012, 06:28 AM)|
|A single larger engine would be cheaper, and can also be more powerful. Also, this might help your design some.|
|low maintenance, and low cost versus conventional construction materials|
|QUOTE (Forza @ May 25 2012, 07:07 AM)|
Tacking on to what Lamoni said, one engine over two is also going to be much better power-weight wise.
Haven't seen anything to suggest Al-Li will be reduce maintenance nor be cheaper than conventional alloys.
|In contrast to new materials systems such as fiber-reinforcedcomposites, low density Al alloys do not require large capital investments by the aircraft producer in newfabricating facilities. This cost savings can more than offset the greater performance increment, whichcomposites may offer, resulting in Al-Li alloys being substantially more cost effective than composites in someapplications. Fatigue crack growth resistance in Al-Li alloys generally is very high; this is important in damage-tolerant structures such as lower wing surfaces|
|QUOTE (Forza @ May 26 2012, 03:05 AM)|
| If you're going to compare Al-Li to carbon fiber composites, be aware you're comparing one expensive alternative against an even more expensive alternative. CFRP's aren't what you'd call conventional; they aren't cutting edge but they are only just starting to feature in aircraft if you understand what I'm saying. |
Al-Li might be more resistant to fractures than other materials but it doesn't eclipse other materials used in aerospace.
|QUOTE (Hurtful Thoughts @ May 26 2012, 06:52 AM)|
|Wasn't there a problem of the M39 leaking burnt powder into the avionics-compartment?|
|QUOTE (Laissez-Faire @ May 26 2012, 02:13 AM)|
|Perhaps pure aluminum, then?|
|QUOTE (Vault X @ May 26 2012, 07:12 PM)|
No one really uses pure metals for structural purposes. Only very rarely.
|QUOTE (Laissez-Faire @ May 26 2012, 10:17 AM)|
I wasn't using the M39.
|QUOTE (Hurtful Thoughts @ May 26 2012, 07:35 PM)|
What sort of [twin] 80 kg 20x102mm revolver-cannon(s) are you using, then?
Also, single-engined F-18E Super-Rhino.
|QUOTE (Hurtful Thoughts @ May 26 2012, 10:15 PM)|
| 1. The M39 has a higher rate of fire than the M621 (1,200 vs 800 rds/min)|
2. All revolver-cannons, being revolvers, have gas-leakage
3. The F-5 went several developmental directions
a. One went straight for a single larger and more powerful engine, and strengthened structure at current size as the F-5G/F-20 for a dedicated-ish lightwieght-fighter.
b. Another re-optimized its airfoil with leading-edge-extensions as the YF-17 for a more multi-role purpose (which attracted Navy-attention since the YF-16 was gunning for the F-20's job)
-Which then was made larger as the F/A-18, and larger-still with the F-18E.
So, to employ the improvements from all into one gigantic package... Most epic multi-role ever... unless we did it in a fly-off against some imaginary Supersized F-16 or F-35...
So now I need to find a turbofan capable of 127 to 190 kN of dry thrust...
|QUOTE (Hurtful Thoughts @ May 26 2012, 10:55 PM)|
| I guess that's what I get when I try replacing a 13-ton F-4D Phantom II and 4-ton F-5E; with an 8 ton YF-17, with a 10 ton FA-18, with a 14-ton F-18E (empty wieghts).|
F-35 weighs about the same class as the F-4D, so the fact that it can VTOL qualifies as a "flying-brick."
Meanwhile, the A-4, A-7, F-20, and F-16 wieghed about 5, 8.8, 5, and 8.5 tons respectively... So it CAN be done.
|QUOTE (Hurtful Thoughts @ May 27 2012, 02:35 AM)|
| Still, the single F404 fanjet of the F-20 produces 70 kN of thrust dry wheras the twin 17 kN engines only make a collective 46 kN at full-afterburner.|
Could also maybe perhaps cross-lock the twin-revolvers, Gast-style [like GSh-23-2] to pretty much eliminate jams.
And finally, GPU-5A (841 kg, 353 rds) or 9A4273 (480 kg, 150 rds) 30mm gun pods. Alternately, FFV ADEN (364 kg, 150 rds).
|QUOTE (Laissez-Faire @ May 26 2012, 08:37 PM)|
The F404 is too big for this platform.
|QUOTE (Danton @ May 26 2012, 09:24 PM)|
This might be helpful. N-300 is a Tiger derivative. You might also want to look at the Northrop-Dornier work in the 80s, like the ND-102 or that design for Argentina I can't remember. ND-102 was supposed to be Mach 2+ with non-afterburning engines, but I can't remember what they were.
|QUOTE (Hurtful Thoughts @ May 27 2012, 04:07 PM)|
| Maximum speed wouldn't increase all that much, since fanjets are high-volume/lower-pressure motors than turbojets. Takeoff-run, rate of climb and ability to maintain airspeed throughout stiff manuvering would improve, though.|
Oh, and maintnance would improve somewhat more if the F404 has parts commonality with your significantly larger airplanes.
|QUOTE (no endorse @ May 27 2012, 08:29 PM)|
|Also check the F414 if you so choose, looks like it's a common engine bay size.|
The turbofan selected was optimized for a higher thrust-to-weight ratio than the F-5 previous, giving the F-12 improved maneuverability capacity, while still being based upon the concepts of the original F-5's turbojet engine. The selected turbofan was a lightweight and military application of the concepts explored by the General Electric F414 turbofan, providing an advanced FADEC-controlled turbofan that used high pressure ratios to forward fuel performance and light weight. The turbofan provides a dry thrust of around 61-62 kN, and total wet thrust of 85 kN.
Length: 355 cm
Fan diameter: 89 cm
Dry weight: 1,079 kg
Compressor: 5-stage high pressure axial
Turbine: 2-stage high-pressure
Pressure ratio: 30:1
Specific fuel consumption:
- Dry: .798 lb/hr/lbf
- Wet: 1.64 lb/hr/lbf
Bypass ratio: .47
The engine uses blated disks in it's high pressure combustor stages to minimize weight, similar to the design of the F414. However, unlike then F414, the engine of the F/A-12 incorporates these blated disks in all it's high-pressure compressor stages (of which there are five). The axial stages act to give the F/A-12's engine an moderately high pressure ratio for it's weight class. In addition, reliability and the ease of manufacturing parts helped reduce the costs of the engine.
The pressure ratio of 30:1 gives the F/A-12's engine more thrust for the weight of the engine, a better specific fuel consumption rate with it's mixture of systems (.798 compared to turbofans usually ranging above .8). These all factor in to key points in engine reliability, high thrust-to-weight ratios, and other factors in the design of the F/A-12 as an air superiority fighter, ensuring maximum performance in a manuever.
The 2 high-pressure turbines compare to the divided 1 low-pressure and 1 high-pressure turbines of the F414, and allow for higher temperatures. The bypass ratio of .5 gives it higher fuel economy than the F414, and thereby the aircraft more performance from the same amount of fuel.
To reduce manufacturing costs, the blated disc fans and the other components were attached using the friction surfacing method of dissimilar materials welding.
|The selected turbofan was a lightweight and military application of the concepts explored by the General Electric F414 turbofan, providing an advanced FADEC-controlled turbofan that used high pressure ratios to forward fuel performance and light weight|
|Additionally, the axial/centrifugal stages act to give the F/A-12's engine an uncommonly high pressure ratio for it's weight class, incorporated from another General Electric design, the CFE CFE738, and was modified for lightweight and ease of military use by the presence of blated disks and other advancements that typically are incorporated in civilian-to-military conversion of engines.|
|These all factor in to key points in engine reliability, high thrust-to-weight ratios, and other factors in the design of the F/A-12 as an air superiority fighter.|
|The 2 high-pressure turbines compare to the divided 1 low-pressure and 1 high-pressure turbines of the F414, and allow for higher temperatures. The bypass ratio of .5 gives it higher fuel economy than the F414, and thereby the aircraft more performance from the same amount of fuel.|
|There are reasons that turbofan engines have a low pressure turbine and compressor in addition to the high pressure systems. I'm not an expert on turbines but I am reasonably sure you need to keep the low pressure component. No endorse might be able to clarify for us.|