Some years back in the old idf forum and in later forums, there was a pic of an IRIAF model of what we called the single engine tomcat floating around. The radome and air intakes were distinctly that of the tomcat but with a fixed wing design with single engine. If you have seen that image, would you recommend that design but as a twin engine frame?
AF of just about every country on the planet starts with a requirements analysis. They ask themselves what do they need, air superiority, airborne air defense, interdiction, multi-role, etc. So it always starts from what an AF requires. Then they look at what options they have, what are their budget constraints, who will sell them which platform, how fast the induction/adoption of the new air crafts, etc. etc.
My current recommendations for Iran, for instance, is based on Iran's circumstances. There are many different things to consider. As you can tell when any members here debate their ideas and their suggestions or recommendations, is (in each case) based on their analysis of Iran's requirements. We are all making suppositions and assumptions, of course.
My own recommendations are based on the fact that Iran needs an indigenous AF air craft as it is falling behind in realistic combat training, keeping up with the latest technologies, planning and testing platforms and tactics against a more superior AF, etc. etc. So hence I suggest that Iran needs to look at all of these, and based on GOOD JUDGMENT, get going as fast as possible and get AF up and running again.
There are also many issues outside of AF to consider for a nation's defense, not just fighter jets, or AF itself.
Whether an air craft is single engine or twin engine depends again on many, many things. First and foremost, since for years I was in charge of OEM maintenance logistics (hence my bias) with air crews from both U.S. and U.K., I look at maintenance and reliability issues. So, if a jet engine is exceptionally reliable, well tested and proven platform, and has very competent and experience maintenance crew, then I would contemplate single engine air craft (outside of other criteria such as range and weapons load).
In almost all cases, a single engine aircraft is set on a logistics BEA, which means that AFs, in the West in particular, use the engine up to 80% of its estimated TBO, and the single engine gets regular checks and regular inspections. Obviously CMA (critical mission application) single engines also have an extra predicated usage scenario such as whether it is used over land, or as a navy application, cost issues, performance requirements, etc. For instance, A4 Skyhawk is a single engine small jet with about 7 ton payload (fuel and weapons), and was used by both Navy and air forces. It was regarded as such a reliable application that it was easily integrated into U.S. Navy.
I have come across maintenance crews who worked on A4 and they say they have never worked on a masterpiece like A4 ever before or after they worked with that aircraft. A4 is an exceptional aircraft in so many way. I don't want to bore you with all the details about its design. But it was an amazing air craft.
Now about single engine F-14 ???
I don't know what overall strategy of Iran's AF is, so it is hard to say one way or the other. Can you build an F-14 with a single engine? I would say, depends.
Here's what most people often miss about air crafts? ....
aerodynamic lift to drag ratio.
If F-14 removed its air intake nacelles and incorporated a redesign to accommodate inlet separation/distortion resulted from crosswind and high angle-of-attack operating conditions, by putting an engine on top (or even underneath still with much smaller air intake for turbojet engines instead of turbofan), it would hugely reduce drag and if the resulting performance is acceptable by the AF for the application they are considering, then it would be perfectly fine and doable.
Let me explain this in a bit more simplistic way.
People always consider that turbofan engines are more fuel efficient (usually about 10-15% or so depending on engines and a few other things), but people hardly ever seem to consider that smaller air intake nacelles reduce drag which can result in fuel savings.
If you have a bigger
turbojet engine (usually above 20,000 of thrust) you can begin to consider and analyze your design based on AF requirements and the higher the engine thrust, the more likely you can have fuel savings from small air intake openings of a
turbojet .
The Su-24 is more efficient in drag than FB-111 although they are roughly somewhat the same size. The former has low drag due to its air intake, compared to the latter's turbofan engines, not considering low flight performance/requirements compared to high altitude flight performance/requirements,
Imagine an F-14, the air intake and bottom engine housing removed, and you had a single R-35 engine on top of the air frame with adequate engine intake variable controller, altitude adjustable air intake, with FBW controls? Taken into consideration weighting coefficient to optimize total pressure loss coefficient and static pressure recovery coefficient, with the external nacelle flow redesign.
That aircraft would be one hell of an aircraft, in terms of flight performance compared to current F-14A that Iran has.
There is very little information available online about F-14A. Most of what you find is about F-14D, which was much heavier and different engines, substantially different.
The Iranian F-14A has engines that are 2 tons each, delivering 20,900/10,850 (afterburner/military) thrust. With 2 engines it delivers: 41,800/21,700 and it weights 37,000ish lbs.
F-14A redesigned as I explained above with a single R-35 would weight 30,000ish lbs, (roughly) with a 29,000/19,000ish engine, with substantially improved aerodynamic lift to drag ratio.
It can also fly at higher altitude.
Look at the numbers above carefully. With a single engine R-35, it can have almost the same non-afterburner thrust for a lighter air craft, and substantially better lift to drag ratio, lower cost of a single engine, better range, and can carry more fuel as a result of lowered weight.
So, the above are just some SAMPLE SCENARIOS AND CONFIGURATIONS that may or may not benefit the AF requirements, depending on what it is. Some AF strategists may decide to go for a single engine air craft with a second engine, so they can rotate the engines and achieve much higher sortie rates, as engines can get rotated out in about 30 minutes allowing the air craft to fly multiple sorties per day.
So the AF has to consider whether single engine or twin is ideal for their requirements, what max take off weight do they need, what weapons load the need, what range do they need, etc. and then decide on the design and configuration.
Swept back wings require more maintenance, but CAN offer (depending on design implementation) much better max take off weight (hence applications like, F-14, FB-111, Su-17/22, Su24, Mig23, Tornado, B-1, Tu22, Tu160, etc. ). It was researched heavily in 1930s by German aviation scientists. All blue prints stolen by U.S. (shared with the Brits) and Russia.
F-14 can also have fixed wing, and can be design with a single or still twin engine configuration.
Also the engine can be brought closer together for design requirements, if needs be.
The engine(s) can also be designed to be placed on top.
Engines on top need to be designed with great attention to a) Inlet flow recovery, b) Inlet flow distortion, c) Inlet Mach distribution. A few other things as well.
With every design, there are pros and cons. So AF requirements have to be near perfect in its crystal clarity, with detailed criteria analysis.
Finally, an AF has to decide with its political branch, and government, parliament, congress, etc. WHAT IS IT THAT THEY NEED AND CAN GET ... once that is clear, then choosing an air craft is much easier.
With regards to Iran, my own opinion is that they need ...
a) A single competent platform with long combat range, with BVR capability, long range missiles, good enough radar/avionics, aerial refueling, secure data link, and hopefully ECM/ECCM/IRCM
b) An air craft that does not cost a lot, is indigenous = 100% maintained and parts supplied, internally inside the country
c) Allows for large numbers to be built, and get our pilots up to date with training, new air combat tactics, and well trained maintenance crews (practice makes perfect)
There are a few other things I can think of, BUT considering where Iran is today, I would be happy with the above.
What platforms can Iran REALISTICALLY develop on its own to potentially deliver the above a/b/c ???
- F-14 can, if the engines are more powerful like AL21F (weighs a quarter ton less each, and has about 25% more afterburner, and 60% more non-afterburner thrust), offering a higher take off weight, more fuel to carry, reduced drag due to AL21F reduced engine air intake, and weight savings. A much better hybrid radar can be integrated with weapons systems like Fakour 90 (hopefully better missiles at the caliber of Phoenix but more modern components with ECM and better thermal batteries, etc.). Iran is already able to do the Wingbox, Swing Wing Servos, Swing Wing Actuators and Spindle. Titanium is an issue, but Iran is currently on a good track with that.
- F-4e can, may be even somewhat easier than F-14. The engines will be the easiest, since AL21F is almost same dimensions as the J79, in weight, length, width and Iran has F-4Ds, they can design radar housing with space for solid state power amplifiers, processors, coolant, oxygen generator, and can develop and integrate the under belly fuel tank. The only problem they have to solve is the weak landing gears (main).
Hope I gave you some ideas, food for thought, potential scenarios, and possibilities.
The design and development and final platform is easy, compared to how hard it is to have a CLEAR DECISION ALONG WITH THE POLITICAL WILL AND THE CAPITAL on what Iran needs short-term to mid-term and what STRATEGIES it is meant to fulfill. Hope Iran AF or AF planners and decision makers have a GREAT JUDGEMENT. I can only pray and hope it is the case.
