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The Making of a Modern Prop Fighter

Posted by tdcoish on December 9, 2019

GUNS ONLY

The romantic image of WW2 involves two fighters weaving around each other, each desperate to bring guns to bear. The reality of WW2 combat is that successful engagements were typically hit and run. As WW2 ace Erich Hartmann said, “I would attack only if I had 2000 meters of clearance above them, then I would come down with great speed…”. This was true of combat between all factions, and was especially prevalent amongst American and Japanese engagements, where later war American fighters massive speed advantage made them near untouchable against the Japanese fighters.

And it’s not particularly hard to understand why. If you are in a much faster plane, should you not like a certain engagement, you can just fly away. You can dive down and make attacks on your terms and, again, just fly away. The effective range of even 50 cals in the air is pretty short, and disorientated and surprised enemy pilots are going to have a tough time getting a return shot in. 

MISSILES

After the war we got both turbines, as well as guided missiles. Missiles have been a game changer. While the exact efficacy of any particular missile is unclear, even with the most pessimistic appraisals missiles bring a few massive tactical advantages.

  1. They can be fired from further range than guns.
  2. They can be fired from a slightly imperfect starting angle. Guns in comparison need to be perfectly aimed to be effective.
  3. They fly faster than any plane in existence, at least forcing a high g turn.
  4. Get kills against unaware opponents.

KILL PROBABILITY

Truthfully, the Pk of missiles is usually greatly exaggerated, as Picard has chronicled time and again on this site. Additionally, real life missile Pk is also slightly inflated, since experienced pilots will refrain from firing their missiles until they have already maneuvered into an appropriate position.

Unfortunately, nobody really knows how effective missiles really are, since realistic testing appears to be utterly refused by the Military Industrial Complex. Before committing to a strategy or vehicle, my first task would be to do thorough testing of missile performance, with remote controlled versions of many different types of planes, including a modern fighter plane, all made cheaply. I’m talking about an all-duraluminum construction with a <5,000 lbs thrust turbojet and a cost of considerably less than a million. These planes need to be cheap enough to conduct effective testing on how effective missiles are from any given distance, altitude, aspect, weather, and many other facets of missile performance. Additionally, the before and after energy state of any given aircraft, as well as the efficacy of counter-measures must also be answered. These questions need to be answered, not just for this proposal, but for the efficacy and overall strategy of any air force.

In any case, using real world data, we know that in the Gulf War, the Americans achieved a BVR missile kill percentage of 34%, while the SAM’s fired at the American Pilots achieved a kill percent of 0.3%. The Iraqi pilots and air force more broadly were, for lack of a better term, totally incompetent. Partly due to their broken equipment, and partly due to their lack of training, they did not react to missiles fired against them. In this ideal situation, a BVR missile still has a ⅔ chance of missing. On the other hand, against a competent opponent, the American Pilots, the Iraqi SAM’s had a 1/300 chance of getting a hit, which should be considered the low end of missile effectiveness.

It is probably true that the Iraqi SAM teams and IADS system as a whole were as incompetent as the rest of the Iraqi military, and a competent military may well have shot down an order of magnitude more planes. Potentially even greater than an order of magnitude. It is also unquestionably true that a competent Air Force would have been shot down at far lower rates than the Iraqi’s were, possibly by greater than an order of magnitude as well. Because we have not yet truly done experiments to find the true efficacy of missiles both in terms of immediate kill potential, as well as energy drained from the victim aircraft, I will have to make assumptions and stick with them for the rest of this article. Assumptions will need to be made both for the outright kill potential, as well as the probability of forcing a high g, energy draining turn. And of course, competence from the attacker and defender is also assumed. 

  1. Pk of a BVR missile, whether fired from the air, or the ground, is 5%. This is probably too high, but 5% is a nice even number.
  2. Pk of a WVR IR missile, fighter to fighter in reasonable position, is 25%.
  3. P of high g turn forced following BVR missile shot, 50%.
  4. P of high g turn forced following WVR missile shot, 100%. (Or close enough that 100% is just an easier number to work with.)

ENERGY DRAINING

Which leads us to our next question, how much does the energy lost in a high g turn or series of turns actually matter? Also, how much energy is lost in any specific plane, for any specific missile shot. Again, these are questions that can ultimately only be answered by repeated experimentation, but some educated guesses can be made. 

Firstly, it is absolutely laughable that high altitude supersonic bombers would remain at high altitude and supersonic while turning to avoid missiles. So laughable that it’s not even worth back of the napkin calculations. However, for fighter planes this is a much more interesting question. If we take arguably the best performing fighter plane in existence, the French Rafale, we have an aircraft that in a totally clean configuration, claims a sustained turn performance of 9.1 G’s. Frankly I’m not even sure that I believe that, but even if true, that’s not supersonic performance. It would be quite interesting to see a chart of any planes maximum sustained turning performance, in g’s, at any given speed, at any given altitude. Again, experimentation is the true method of knowledge, but we can make some educated guesses here.

The definition of cruise speed is the speed for any given altitude where dry thrust and drag are equal to each other. For the Rafale, the combined dry thrust of the two engines is 22,400 lbs. The cruise speed depends on the altitude, but at high altitude the cruise speed is reportedly about 1400 kmph. The maximum speed of the Rafale at low altitude is only 1,390 kmph, in clean configuration, with full afterburners. At high altitude cruise, the Rafale is generating 22,400 lbs of thrust, and 22,400 lbs of drag. Any turn at this speed will generate considerable extra drag, slowing the aircraft. Meaning, that at this speed the maximum sustained turn g’s is 0. That’s not quite true, since we can throw on the afterburner, but I hope the example makes the concept clear.

Since it was incredibly difficult to find an Energy-Maneuverability chart for the Dassault Rafale, I looked up the F-16 instead. Turns out it’s incredibly difficult to find an EM graph for the F-16. Same for the F-18. Frankly, it’s almost impossible to find out the specific energy loss from any maneuver at any speed or altitude for any specific aircraft. I suspect that these are out there somewhere, they’re just not released to the general public. I would very much like the raw numbers, so that I could calculate the specific excess power, which would be massively negative, for, say, an F-16 at 20,000 ft and 1300 kmph pulling a 9G turn. If we had the specific excess thrust, which again would be massively negative, then we could calculate the actual deceleration experienced by our F-16. Unfortunately, until then we’re just going to have to make do with educated guesses. The lift-drag ratio of different fighters is going to be vastly different, and may change depending on the angle of attack and airspeed, but we can go ahead and pull out a ballpark figure. 

  1. For our generic fighter plane example flying at cruise speed, we will assume a 9G turn will result in a deceleration of 5G’s. That’s 50 mps/s, or 180 kmph/s. This will of course depend on the fighter design and configuration.
  2. For our generic fighter plane example, we will assume a maximum sustained turn rate of 6G at 800 kmph.

Again, I wish I had access to better data in order to find these results, but this is all we have. Anecdotally a deceleration rate of 180 kmph/s fits with the described behaviour of fighter pilots who have actually evaded missiles, and talk about rapidly losing speed and altitude. Obviously the net drag decreases as the plane flies slower, but this should be used as a general ballpark figure. With that in mind, a fighter pulling 9 G’s for 3 seconds is going to lose approximately 540 kmph. This is assuming a supercruise speed of, say, 1400 kmph. 

Since a three second turn can be thought of as close to the minimum turning time for a fighter to avoid a missile, we can think of any successful missile shot that does not result in a kill as bleeding 540 kmph or the equivalent in altitude from the victim fighter plane. Extending this to a speed below 540 kmph gives us a nonsense result, no fighter pilot will, unless extremely confused, drive his plane into the ground or reduce his airspeed to zero. The latter is in fact, not physically possible, a plane will not be able to pull 9g’s below a certain speed for any given altitude. 

However, this does show that a plane can, depending on its aeronautical performance, be reduced to an extremely vulnerable energy state, through successive missile shots. An F-16 needs to move at just over 200 kmph on the runway in order to pull 1G of lift and takeoff. The F-16 cannot pull 9 G’s, it’s maximum, until over about 650 kmph. Beneath that speed, the plane cannot pull 9 G’s at all, no matter how much angle of attack is pulled by the pilot. At speeds of mere hundreds of kmph, jet fighters flub their way through the skies, with their razor sharp delta wings being unable to generate the lift required to turn. 

AIR SUPERIORITY VS K/D RATIO

There is another very understandable misconception WRT fighter planes, the idea that the true measure of a fighter plane is its ability to fight other fighter planes, specifically measured through the exchange ratio. It is understandable why this idea exists, but it is extremely misleading. The problem is that air superiority is not an advantage unless over geographically important terrain. 

Consider an extreme example, an aircraft carrier on the open ocean. Having air superiority, even uncontested air supremacy, is entirely irrelevant over the vast majority of the oceans. In fact, any nation with enough money to buy a single Cessna 172 with some guns and floats attached to it can get uncontested air supremacy over the vast majority of the ocean, if for no other reason then that nobody would care to contest. On the other hand, if we have Nation B using fighters to escort some bombers into range to destroy Nation A’s aircraft carrier, well then it seems a lot more important to outright get kills then to minimize the risk to the pilot. If Nation A’s pilots fire some long range AAM’s from a safe distance, and then go home, it really doesn’t matter how many kills they got unless it was close to 100%, since they’re about to have their carrier bombed and destroyed.

Let’s consider another example, the US has entered a civil war, West vs East, with both sides having roughly the same level of technology and manpower. Let’s say that West has decided to do a serious attack on, say, an East airfield. In fact, to make this more extreme, let’s say that this is an airborne attack, where the attackers need to be dropped in massed troop transport helicopters, and, due to the geography, both sides will need to be resupplied through the air. Additionally, both sides have CAS in the form of Apaches and A-10 Warthogs. 

To give some numbers, let’s say that we have 4 fighters on each side, F-16’s, and many many other aircraft, let’s say 100 in total. However, East has developed a new AAM which can be fired from 120 km’s away, magically knows where all the enemy fighters are, and has a Pk of 2%. Due to this, and the idea that what’s really important is having a nice K/D ratio, the East’s fighter pilots load up with 8 missiles per fighter, go out in pairs of 2 and fire off all 8 missiles at the West’s fighter planes, which are also going out in pairs. After firing these missiles, East’s fighter planes turn around and go back to base. The odds of getting a kill is pretty low, even with that full salvo, less than 20% in fact, but hey, if they can’t attack us back, we’re going to get a great exchange ratio right?

That’s actually true, but in that example our fighter planes did not accomplish much of anything, whereas the West’s fighter planes could be used to:

  1. Destroy our A-10 Warthogs
  2. Destroy our Troop Transport Helicopters
  3. Destroy our cargo planes
  4. Destroy whatever the hell they want, since when we flew away, we conceded total Air Superiority

From the perspective of the attacking West Ground Forces, they got the benefit of A-10’s and Apache’s finding and strafing the enemy, reinforcements of other troops, and bountiful resupply of ammunition and food. In contrast, East’s Ground Forces had no air support, no reinforcements, and were starving and out of ammo. That sounds like a rout to my ears. I hope we didn’t need that air base for anything. 

But hey, after enough missile salvos the East forces finally got a single F-16/FLX! So it was totally worth it. Sarcasm aside, it is worth mentioning that ground based AA defenses are still valid and effective, so East wouldn’t have been quite as disadvantaged as previously thought, but it’s going to be a lot harder to win any battle if your fighter planes are useless.

I picked an air base for a reason, but this applies to any strategically or operationally important target on the ground. I chose an air base to illustrate the strategic element of air power. When the Germans conquered France in 1940, they didn’t destroy French Air Power through a slow process of many weeks or months of whittling them down through 1v1 air duels. They destroyed French Air Power by capturing strategic locations on the ground, like manufacturing plants, fuel depots, and airfields. Because when Hans drives his tank onto your airfield, it stops being your air field. If a fighter plane does not meaningfully contribute to the achievement of Air Superiority explicitly for the benefit of Ground Forces, then it has not meaningfully provided value to a military. A fighter plane that does not shoot down or at least scare away enemy non-fighters is worth nothing.

As an aside, it is safe to say that even if missiles were the be all and end all of fighter to fighter engagements, you would still want an onboard gun to mop up the rest of the aircraft you come upon, should you run out of missiles. Which makes the idiocy of the USAF not installing guns on some mid-70’s fighters all the more embarrassing. 

STAYING POWER/ENDURANCE FIGHTER

While it is obviously incredibly important to be able to at least defend yourself and other friendly aircraft against enemy fighters, if we wanted to design a plane that was only useful against non-fighter aircraft, what would we design? A look to the original EMB-312 Tucano shows us roughly the archetype of what I’m calling an Endurance Fighter.

The plane was originally designed to fight the drug war in South America, specifically to monitor Brazilian airspace for civilian airplanes smuggling drugs across the border. To that end the plane was given a reasonably fast cruise speed, 440 kmph, very nice range, 1900 km, and a reasonably high g loading, +6/-3. The mission of the plane was to fly back and forth over Brazilian airspace visually looking for Pablo in his drug smuggling Cessna 172, as part of a system also involving ground radars and an airbourne radar in a different plane acting as a sort of AWACS. 

For armament the Tocano was given .50 cals, although I believe they had to be attached in a pod, as opposed to built into the wings. The pods could also carry some small bombs and rockets, although that was just for attacks of opportunity against ground targets, and not particularly transferable. The flight ceiling was 25,000 ft, which again is plenty for the low flying cessnas it was designed to track down and intercept.

We can see that, while not perfect, if simply transported directly into a military, the Tocano would be a menace to pretty much everything that’s not a jet fighter. High altitude bombers would have little to worry about, but every helicopter, CAS airplane, cargo plane, drone, and other aircraft would be prey to such a plane. The modern Super Tocano is an even better example, with a higher cruise speed, 520 kmph, over 8 hours of endurance, almost 3,000 km’s of range, and slightly higher g tolerances. 

It’s not perfect of course. What we would want for our Endurance Fighter is the ability to carry short range IR missiles, and quite a few of them. We may or may not want a second seat in there, only the pilots could know, with the performance advantage of a single seater not being quite as absolutely crucial as in a regular fighter. 

WRT the IR missiles, we can have them be considerably slower than traditional IR missiles, and gain maneuverability or range as a result. Since we’re using these against helicopters, CAS aircraft, cargo airplanes, and other utility airplanes our missile does not need to be fast in order to “catch” the target. A section below details the design of these missiles. What’s more important is the number that we can carry, giving us the ability to engage targets from a further distance, which may be tactically necessary to avoid return fire.

It should be noted, the overall goal for our Endurance Fighter is to supplement our Jet Fighters in an area, to bully and destroy enemy non-fighter planes. An example mission would be the imaginary airbase attack detailed above, where our Endurance Fighter, let’s call it EF-1, could be constantly in the area trying to ensure no enemy aircraft could operate, even while our Jet Fighters have to go back to base to refuel. As a result, a force of 4 Jet Fighters, which can be in the area for 1 hour every four hours, and 4 EF fighters, which can be in the area for 8 hours every 12 hours, can combined provide much more efficient and effective combined air superiority.

TURBOPROPS?

All of this begs the question, how low can you go? Since we’re just bullying the plebs of the skies, fairly low indeed. The fastest helicopters fly at just a touch faster than 300 kmph. Even the original Tucano can catch any helicopter with ease. CAS airplanes like the A-10 and the SU-25 can cruise at speeds of over 500 kmph, with the SU 25 being even faster. This is of course entirely irrelevant. The A-10 cannot be useful at its cruise speed, only if it is turning and patrolling in an area. While it is nice to have a higher cruise speed, close in turning ability and missile loadout seem to be much more important, as our IR missile will be easily able to chase down an A-10, or even an SU-25.

A turboprop is massively more efficient at low speeds and altitude, potentially as high as 2-1, when at low speeds. Testing with propellers on stands gives us a SHP to thrust conversion ratio of between 3-1 and 3.5-1. Taking a low end approach, if we use the PT6 1600 SHP engine, we should be producing roughly 4800 lbs of thrust. With reasonable rigor in design, and not too much junk added to the plane, it should be possible to create our EF-1 with a T/W ratio approaching 1, so the plane would not be underpowered at low speeds and altitudes, although props drastically lose power after ~750 kmph, so there is a harsh limit to the ultimate speed of our airplane. Our turboprop airplane will have a massively improved endurance advantage over a jet fighter, and should not sacrifice significant acceleration at the low speeds and altitudes that it is designed to operate in.

In fact, if we forced a jet fighter to fly at speeds of 700 kmph or slower, the EF-1 would massively out-turn and outfight that traditional fighter. This leads to a very interesting question, if it is true that successive missile shots can reduce pretty much all planes to a low altitude and speed, can the missiles carried onboard the EF-1 reduce a genuine jet fighter, such as the F-16, to an energy regime that our EF-1 can outfight it in? 

CHASE POTENTIAL – LONG RANGE

For our EF-1 to have a chance at all, what we want out of our missiles is to force the enemy fighter plane to turn, and to turn hard, or to die. For starters, that necessitates our missile actually reaching the enemy plane, ignoring a pilot who sees the missile and turns just in case despite being out of range. This is one of those times in my life where I really wish I knew calculus.

Let’s start with the absolute worst extreme. We’re flying south at 750 kmph, and the enemy fighter plane flies by us at 1,800 kmph. By the time we’ve turned around to face them they’re already 10 km away, still flying obliviously at 1,800 kmph. I think this is one of those times where you maybe can’t really expect any missile to make up the distance, no matter the size. If we fire the missile it is going to lose a little bit more distance until the speed equalizes, then it needs to make up the gap from there. I truly question whether the AIM-9 or the ASRAAM can actually make up the distance before running out of fuel, considering the AIM-9 has a whopping 2.8 second burn time. The ASRAAM may fare better, with its two stage engine, and actually have enough maneuverability to force a hard turn. Even then it’s very questionable.

It was at this point that I was thinking of a small ramjet powered missile. Since rockets carry oxidizer amounting to about 3.4 times the weight in fuel, a ramjet engine should theoretically have far greater range. This also isn’t a particularly new concept either, the MBDA meteor missile has a ramjet second stage, and SAM’s with ramjets go at least back to the Talos missile back in the late 60’s. However, I have since backed off on this concept, because there are some problems with a ramjet. First, the minimum speed requirement of a ramjet means that we are going to need a booster stage for reliable ignition. Second, the placement of the intake increases drag on the missile and the airplane it’s attached to. Third, a ramjet apparently has internal structural requirements, since you need to have a very precisely made engine, or multiple engines, for the structure to work. There are very valid reasons why, despite inventing them in the 60’s, both the Americans and Russians/Soviets do not currently produce or field a single ramjet powered AAM or SAM. I do think a project to create a ramjet missile should be undertaken, but this is something that should absolutely be attempted with the belief that the odds of success should be considered low.

Taking a step back, if an enemy fighter is out of range of even short range IR missiles, then even if we had a long range IR or radar missile that could force the turn, it’s entirely unlikely that our prop fighter could actually make up the distance anyway. Ultimately, this is what probably kills the concept for me. Missiles can make up a great deal of energy, but there is a limit. It isn’t hard to believe that a plane such as the F-22 or Rafale to be cruising along at around 1500 kmph, detect the EF-1, make a little turn for an attack at 5km distance, and then fly away. Even if the turning for the attack takes the speed down to a subsonic 1100 kmph, the distance and speed difference between the two airplanes is probably insurmountable. This should be recognized as different than an enemy spamming low percentage long range missiles at you and then going home. In this case, the enemy fighter plane can engage and disengage at will, which is a legitimately big advantage, probably insurmountable.

It is also true that 1v1 engagements are to be considered the exception rather than the rule, and the same resources will bring nearly twice the number of turboprops to the arena as opposed to jet fighters. So a more realistic question would be, can the prop fighter defend itself against jets in a 6v4 engagement? Again, experimentation must be conducted, I just don’t think that the massive energy disadvantage can be overcome.

CHASE POTENTIAL – SHORT RANGE

The second missile we need to make is the short range missile. Designed to essentially keep an already low and fairly close fighter plane from taking off again. Used in the range barely beyond guns, or perhaps up to 5 km or so against a low energy fighter. What we want is a missile with a top speed of around M1.5, a burn time of 2 seconds or possibly even less, and the previously specified range of 5 km. We are going to need some maneuverability after the rocket has gone out, but the R-60 looks moderately close to what I’m looking for. The Wikipedia stated range of 8km is probably very optimistic, but in reality it’s still good enough for our purposes. I would definitely sacrifice a lot of speed (M2.7) for bigger fins and longer burn time, which is going to both give us better range for any size, and better post-burnout maneuverability. We really don’t care about speeds, and in fact higher speeds may be a bit of a drawback here, since it simply lengthens our turning radius, which in this case is quite poor, since we are trying to force very hard turns on slowed fighters.

This missile is our workhorse. In fact, I am calling it that, the AAM-2 Workhorse. The low speeds, high maneuverability, and sustained burn giving good range (for its size) are exactly what we want not just on low-energy fighters, but also on everything else in the sky. The final design calls for something with a budget of about 100 lbs, a burn time of 3 seconds, maximum practical speed of around M1.5 (maybe even lower), practical range < 5km, and optimized for less than 10,000 ft altitude. I feel like once a fighter, even the Rafale, has been “caught” inside the effective range of the AAM-2 Workhorse, and is forced to make constant hard turns, the advantage would have to go to the prop fighter. In the meantime, the R-60 will serve as a good enough version of this concept.

For this missile especially, serious thought must go to the idea of getting rid of the explosive and replacing it with a penetrator. This would save weight with the Chaser, which is especially important on a wingtip missile. The saved weight has a positive spiral effect, where we would also need a little less fuel, and a smaller motor. For the Workhorse, we wouldn’t save much weight over something like the warhead in the R-60 (6.6lbs), by going to something like a 5 lbs penetrator. I don’t know what the weight of the proximity fuze is, but I can’t imagine more than 5 lbs weight savings all told. Really, the question is simply one of efficacy. We can hypothesize, but only realistic testing with drone targets would tell us the answer here.

TEAMWORK MAKES THE DREAM WORK

Of course, as I mentioned previously, all written above gets massively more complicated, and in favour of the prop fighter, when we crowd the skies. If we imagine some totally artificial 1v1 duel with infinite space, then a jet fighter gets a massive advantage. On the other hand, if we imagine a 4v4, and especially with numerous helicopters, CAS planes, recon aircraft, and other targets in the area, the question becomes a lot more interesting. Especially when the area of interest on the ground or ocean is very small. Additionally, due to the increased endurance, for the same resources, at least in terms of pilots and fuel, you would have significantly more force presence in any area, which would give you a large advantage. 

Having said that, a small subsonic cruiser jet fighter would get you many of the same advantages, while providing little to no tactical disadvantages. Using the Folland Gnat as an example, with modern materials and engines we can almost certainly make a jet fighter with a loaded weight of 5,000 lbs or less, with thrust of 5,000 lbs or more. Such a fighter would also naturally consume very little of the nations fuel, and could be designed to have very good range and endurance. 

PROBLEMS/NON-STARTERS

Unfortunately, there are some serious problems with the prop fighter concept that probably make the very concept a non-starter.

A prop makes it incredibly difficult to put in a radar, or IRST on the airplane. Although radar, which gives your position away, is probably somewhat overrated in fighter to fighter engagements, if trying to hunt down enemy non-fighters, finding them in the first place becomes much more important. Radar pods could be strapped on, but not without adding a painful amount of drag.

In order to get the high speeds that we want, sacrifices must be made. If we want a plane with 700+ kmph cruise speed, then we’re going to be using thinner, higher aspect ratio wings, and a lot less wing in the first place. That is going to leave less room for guns and fuel, which will cut into our range and endurance, and make things less workable. It will also leave us with a higher takeoff and landing speed, less lift for any given speed, and generally worse handling characteristics. 

The plane needs to be armoured anyways. A plane flying within guns range of the ground, which this plane absolutely would be much of the time, is going to be getting ground fire. We can’t get away with no self-sealing fuel tanks and no cockpit armour. To do otherwise is criminal negligence. What that means is less room for fuel, and a heavier airplane. I can’t quantify how much worse the plane would be after being armoured, but if you need to throw something like a 1200 lbs bathtub in there like the A-10 has, that pretty much sinks the concept in and of itself.

Propellers themselves have hard limits. The Jet Fighter that this made me think about making, my FLX so to speak, is considerably slower in cruise than Picards FLX, due to the work I put in trying to make this plane. However, it still cruises at over 1,000 kmph, and will be supersonic capable. Propellers run into hard efficiency limits around 750 kmph, and even that speed is not possible with the design of the EF-1. At the lower speeds, the plane just doesn’t have quite enough speed to fight actual fighter planes, at reasonable exchange ratios. Against an idiotic opponent who fires missiles and leaves, this might be fine, but against a serious, competent enemy, that’s just not good enough. As mentioned earlier, the energy disadvantage is probably insurmountable.

It’s harder to install a gun on a plane like this. Or more specifically, putting guns in the wings has drawbacks. Even my CAS plane just has 50 cals, and making wing guns converge is not the end of the world, but the guns and ammo take up space in the wings, leaving less room for fuel.

High power single engine turboprops are dangerous. The torque created by powerful single engine prop airplanes has been known to rotate the entire plane over and cause a crash. This isn’t an issue with counter-rotating dual prop airplanes, since the torque from one cancels out the other. The vanilla proposal, without armour, would be by far the plane with the highest SHP/Weight ratio of any single engine turboprop ever, which might be too dangerous to fly. Takeoffs and landings would be very dangerous.

MIGHT AS WELL BE CAS

This final drawback gets its own section, as I believe this perfectly describes the problems with this plane and others like it, such as the Super Tucano, from a stepped back perspective. A secondary role that this plane serves is as a ground attack and reconnaissance airplane. However, if used in that role, the single engine turboprop is probably a non-starter. I personally would not fly the EF-1 in ground attack nearly as aggressively as I would fly my version of the ALX in ground attack/air reconnaissance. 

Additionally, even ignoring the single engine, if we’re going to add all the extra armour and self-sealing fuel tanks, we might as well add a fly by wire backup control scheme and figure out a way for it to land if the retractable landing gear won’t go down. On top of that, the requirement for a very high cruise speed is irrelevant, and the sacrifices to low speed handling and loiter time are unjustified. While I’ve come to believe that high munitions load has numerous drawbacks, if we do want a tactical bomber, then we can build a much better plane than this. 

So what we’re left with is a CAS plane that is, relative to a real CAS plane, dangerous to fly, sluggish to control, poorly armed, and logistically intensive. On top of that, in order to make ourselves functional in that role, our range and endurance would have to take a large hit, partly ruining a lot of the point of the airplane over a traditional jet fighter. Finally, my ALX is a real STOL monster, capable of taking off and landing in short, rough fields. There’s absolutely no way you could possibly make a high speed cruiser magically generate enough lift to take off at low speeds from rough fields, especially when loaded down with armour.

But ultimately what really kills the concept, is that a beast of a CAS plane, also serves much of the role that the EF-1 serves as a Worlds Best Anti-Aircraft Artillery, or King of the Hill Air Superiority Fighter, or Endurance Fighter. If what we want is something that can bully enemy non-fighters, such as helicopters, out of the area, it may well be almost as good to have a dedicated CAS airplane. While the EF-1 would be making sweeps through an area and then doubling back, my ALX would not nearly have the speed to work that way, but you could just send them to an area to support Ground Forces, and then just tell them to destroy any flying hostile they encounter. If a battle is taking place over a small area of land, if the enemy wants to fly helicopters into there, then it doesn’t matter much if your cruise speed is 750 kmph, or 250 kmph, they have to come to you. 

So a CAS plane that’s designed from the ground up to be a constant menacing presence over the battlefield will probably be good enough in that role to push out any serious niche for the prop fighter. A traditional Jet Fighter can cover an even larger amount of ground when sweeping through an area, and since we will already have Jet Fighters, the range upside versus a traditional CAS is lessened. Since a tough CAS plane can be even more persistent, while offering a lot more as an actual CAS airplane, there’s just not that much room on either end for the EF-1. If you want lots of ground covered and a plane that can dominate everything that flies, make yourself a Jet Fighter. If you want a plane that can provide excellent scouting and fire support for ground forces, build yourself a CAS. If you want a plane that is very mediocre at both, build yourself a prop fighter.

DEFENSIVE/INTEGRATED AIR DEFENSE SYSTEM

There is however, two possible niches remaining. First, while offensively it does appear that there are too many limitations to make the concept really worth producing. However, as part of an Integrated Air Defense System this plane could have a very valid niche, as a sort of Worlds Best Anti-Aircraft Artillery. Since the entire purpose of the ground based radar system plus SAM’s is to bleed energy from incoming hostile aircraft, something like the EF-1 probably has a much more valid role as the cleanup crew for incoming aircraft. The speed disadvantage is greatly lessened in importance, and the sheer presence in the sky has much more meaning when trying to stop what could very well be massed attacks against your cities/factories/interior military bases. Additionally, the lack of radar is nowhere near as important, since the ground based radars should be feeding the information into the plane. On top of all that, lack of armour is acceptable, since the ground underneath should be friendly ground, and taking ground fire a very much reduced risk.

Secondly, as a naval strike airplane the EF-1 has an argument. The very low speeds of my ALX are not necessary for finding things on the ocean, because they are not camouflaged soldiers, but boats floating on water. There is also a great deal more of an argument for range in and of itself, as opposed to persistence, since we are again, trying to find things on the open ocean. Finally, for tactical purposes, I would prefer to be in a faster plane as opposed to my ALX, since the low speed does not serve any real tactical purpose, and the same for the low speed maneuverability. The increased speed, possibly as much as 3x faster cruise speed, is a very real benefit in getting to a target quickly and avoiding SAM’s and AAA. 

JET FIGHTER

I am extremely happy that I decided to take the time to flesh out my thoughts and research things as I did, if for no other reason that it sharpened my designs for my FLX and ALX. As far as a Jet Fighter is concerned, I’m leaning a lot closer to something like a modern, dynamically unstable, and even lighter version of the A-4 Skyhawk, or the F-5 Tiger. Spiritual successors, more than evolutions of those specific designs of course. 

The main reason being that persistence over a combat area is way more important than I had previously realized, and finding and destroying enemy non-fighters is also more important than I had previously realized. To that end, a small onboard radar is an absolute must, since finding enemy non-fighters carries a tremendous amount of value, that may often be worth a pulse or two. IRST could well replace the radar, but I think that the all-weather and low-altitude advantages of radar make me lean towards a radar. Supercruise is definitely not on the table, due to the increased fuel consumption decreasing range and especially endurance. Instead, the aerodynamic design will have thicker wings, less sweep, and more wing, so as to generate more lift at all speeds, at the expense of max and cruise speed. The F-16’s cruise speed of between 790-1035 kmph is definitely the region we’re going for here. And in fact, a miniaturized F-16A would be the closest existing plane to what I want.

CONCLUSION

Boy that was a lot of work just to come to the conclusion that a turboprop fighter plane would be a very niche role aircraft. Ultimately, against a competent opponent, a fighter plane must be able to at least distract and chase away their fighters, while having the persistence, agility, and ammunition, to make multiple sweeps and kills against their other aircraft. Because of the inability to accomplish the former, the EF-1 may well not justify its own existence. I don’t think that a turboprop fighter should be built for anything other than niche roles where it’s disadvantages can be hid.

9 Responses to “The Making of a Modern Prop Fighter”

  1. tdcoish said

    Picard,

    Writing this really cleared my head WRT my version of an ALX/OLX plane. I can give you a write up on that as well. If you’re interested, the cliff notes are:

    1) STOL performance is incredibly important
    2) Hanging ammunition is very overrated and potentially dangerous
    3) A great CAS plane is also a great OLX, and there is no reason for both
    4) Double engines are a must
    5) 30mm cannon is no longer worth the weight and recoil penalties
    6) 50 cals are the best blend of weight/efficacy for the vast amount of targets
    7) Many forms of firepower are unrealistic
    8) The plane should be tiny, easily less than 8,000 lbs, preferably less than 5,000 lbs. This is possible.
    9) The smaller weight allows us to use piston engines, in the 300 hp range for both, without being overpowered.
    10) Piston engines give us even greater endurance
    11) Drastic change in doctrine, ALX should be almost as common on the battlefield as an APC.

    And a few others.

    Like

    • picard578 said

      Yeah, that would be fine. If you need help/inspiration, you may take a look at this, even though it is not a prop fighter:
      https://www.deviantart.com/blacktailfa/art/Vought-VB-100-Blitzfighter-296126107

      I am writing an article on A-10 right now, but I’ve been in over my head so it stretched for several months instead of a couple of weeks…

      Like

    • Alex said

      If you’re interested in piston-engine CAS design, perhaps you could go back in time to one model that was like the A-10 of it’s time — the Henschel Hs-129.

      – Twin engine (700 hp at take-off each)
      – Armored cockpit against 12.7mm steel core DShK ammo (windshield 75mm thick!)
      – 315 km/h cruise speed, 150 km/h stall speed, 395 km/h max level speed at 3000m, 670 km/h dive speed limit
      – 3992 kg empty weight, 5170 maximum takeoff weight, 450 kg fuel
      – 2x 7.92mm MG + 2x 20mm cannons internally
      – Mission specific central mounting plate with options for bomb racks or conformal 30mm anti-tank cannon (+wing bomb racks)

      Like

  2. Alex said

    Looking at the Embraer Tucano, I’m thinking how much it reminds me of P-51. The wings are similar and the tail is very similar.

    Modern turbo-props like the Pilatus PC-21 have power and weight close to the WW2 fighters like P-51 and late Bf-109 and very similar max. and stall speeds and climb rate.

    Perhaps it is beneficial to have a mix of different tools for different tasks… A light prop fighter armed with missiles and passive sensors, data-linked to ground or airborne radars (or other sensors), can be difficult to spot, yet deadly. Even the thought that there might be dozens of those, lurking in the area, might be enough for the enemy to reconsider his plans…

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    • tdcoish said

      This is very true, but as I stated in the article, I’ve come to believe that a subsonic cruising jet fighter mixed with massed CAS planes serves the same purpose, with a drastically higher upside. While it is true that dozens of Super Tocanos armed with missiles would be a very scary threat to any enemy planes, the same would be true for dozens of CAS planes, which also have the benefit of being armoured and survivable against ground fire, as well as the obvious benefit of being built for CAS in the first place.

      Additionally, and I didn’t do a great job explaining this, but part of the perceived advantage is the small size. However, that’s just because modern jet fighters exist to rob the taxpayer as opposed to winning wars. You can build a tiny jet fighter, in the 5,000 lbs area, which, on a strategic level, also has the benefit of very little fuel consumption per sortie. So the small size of a prop fighter versus a real jet fighter is a red herring.

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  3. Alex said

    Have you seen this diesel engine — https://en.m.wikipedia.org/wiki/RED_A03 ?

    Like

  4. Altandmain said

    One other consideration for endurance is the fuel fraction, if only for the long term endurance of the aircraft. For that reason, I am pro-delta wing for the fighter, although for the CAS aircraft, one drawback of fuel in the wings is the vulnerability.

    Like

    • Alex said

      Usually the fuel from the wing tanks gets depleted first. And jet/diesel fuel is not so easy to set on fire as was gasoline in WW2 aircraft.

      Like

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