Aside from the AT-6B Texan II, another aircraft worth considering in the turboprop Light Attack Aircraft market is the AT-802U. This aircraft is interesting because it made claims about long endurance, high payload and excellent ballistic protection to make it a good candidate for the Philippine Air Force’s (PAF) planned Close Air Support (CAS) acquisition. Hence in this blog, I will be comparing it to the established leader of the turboprop attack aircraft market, the A-29B.
The EMB314 or A-29 is made by Brazil’s “Embraer” company, it is a turboprop aircraft designed for light attack, Counter Insurgency (COIN), CAS and Aerial Reconnaissance missions in low threat environments, and also for Pilot Training. It is based on the EMB312 Tucano Trainer aircraft, but has a longer fuselage, more powerful engine and strengthened airframe. It first flew in 1999, and since then over 170 aircraft has been built and went into service in 11 countries around the world. The A-29B is the two-seat version of the aircraft, and its official nickname is the “Super Tucano“.1
The AT-802U is made by the American company “Air Tractor Incorporated“, and it is also a turboprop aircraft designed for the light attack role. It is based on the commercially successful AT-802 of which over 500 aircraft have been built and served in civilian markets all over the world since its first flight in 1990. The AT-802 is claimed by Air Tractor as the current largest agricultural aircraft in the world and is used mainly for crop dusting or fire-fighting purposes.
The AT-802U is the special armed version of the AT-802 with engine and cockpit armor, a bulletproof windscreen, self-sealing fuel tanks, and structural reinforcements which first flew in 2009, and its official nickname is the “Air Tractor”. Its first and only customer so far has been the United Arab Emirates who bought 10 aircraft which were all delivered in 2011.2 3
Things get a bit confusing from hereon for the AT-802U because the US company responsible for weapons and systems integration for the Air Tractor, Iomax, has also launched a COMPETING aircraft design based on the Thrush 710 made by another American company, “Thrush Aircraft“. Reports say that Iomax chose the Thrush 710 because it allowed them to make changes in the production line as necessary, something they reportedly are unable to do with the AT-802. Both the Thrush 710 and AT-802 are based on the same aircraft design made by Leland Snow, hence they look almost exactly the same but with small differences.4
Iomax named their armed version of the Thrush 710 as the “Archangel“, and I initially thought of using it for this comparison, but the problem is that I found Iomax to be less than complete in terms of providing information about their aircraft, unlike Air Tractor wherein they provided complete details about the AT-802U (which they still market in their website). If you go to Iomax’s website for the Archangel,5 for example, you won’t find important details like Empty Weight, Wing Area, Maximum Speed, etc. I tried to ask these from them, but they never answered back.
Perhaps Iomax is just more “savvy” (deceptive?) as some of these information do reveal the WEAKNESSES of their aircraft, as we shall see later on. At any rate, the performances of the Archangel and AT-802U should be very similar, and in fact the AT-802U might even be slightly better because it has a heavier take off weight and a lot more pylons (eleven as opposed to only seven) than the Archangel.
For the “Maneuverability” and “Payload and Range” sections, the following considerations were made:
– Weights with 100% internal fuel was used to try to simulate the aircraft going into combat with full internal fuel after dropping their External Fuel Tanks.
– The weights of the armaments were not included as the RATIOS and DIFFERENCES BETWEEN BOTH AIRCRAFT will remain the same if they will be armed with the same type and same number of armaments.
– Data for each aircraft was derived from various websites at 6 7.
For both aircraft’s maneuvering capability, I am looking at their WING LOADING* and POWER TO WEIGHT RATIO.* I would’ve wanted to take a look at more aspects like Stall Speed, Maximum Alpha, etc., but those data are hard to come by for both aircraft. Hence, these should suffice for now. Remember that a lower Wing Loading means the aircraft can turn tighter and vice-versa, and a higher Thrust-to-Weight Ratio means the aircraft can go faster going straight up or straight down and vice-versa. I did not include the criteria of LIMIT LOAD FACTOR as I could not find any references in the internet about the AT-802U’s G-limit. For some reason, the manufacturer did not publish it.
– WING LOADING: A good 22% advantage for the AT-802U over the A-29B
– POWER TO WEIGHT RATIO: A huge 57% advantage for the A-29B over the AT-802U
+++ Despite the fact that the AT-802U is almost 60% heavier with a full internal fuel than the A-29B, it has a lower wing loading by virtue of its large wing which is an impressive 92% larger than the A-29B, hence “soaking” off much of that weight over a larger area. A caveat, though: Air Tractor did NOT publish the G-limit of the AT-802U, and if it turns out that it has a lower G-limit than the A-29B, then that advantage of lower wing loading maybe cancelled off altogether depending on how large the difference is.
+++ Unfortunately for the AT-802U it only has the same engine power as the A-29B, and all that added weight results in a much lower Power to Weight ratio and thus lower performance in terms of climb rate or dive speed.
+++ I did not bother to compare the maximum speeds of both the AT-6B and the A-29B because they were very similar, only a couple of kph apart. However, in this case I had to publish it because there is a LARGE difference in speed between the two aircraft at 50% or almost 200 kph difference. The reason for the AT-802U’s lack of speed is mainly because of its LARGE WING: It soaks up the weight of the aircraft for a lower wing loading, but it also creates a lot of DRAG. Couple this with its large size and heavier weight, it results in a lower maximum speed for the aircraft using the same engine power. Speed is critical because:
– A faster aircraft will reach the combat area SOONER
– If an aircraft is too slow, it will be easier to hit and thus more vulnerable to anti-aircraft fire
– Higher speed means more Kinetic Energy during launching of weapons enabling some missiles and bombs to have longer range
– INTFF: A very impressive figure of over 200% for the AT-802U, indicating that it can travel a full 2 times further than the A-29B.
– PAYLOAD: Favors the Super Tucano at full internal fuel as it can carry 30% (355 kg) more load than the AT-802U.
+++ Excellent fuel load for a prop-driven aircraft with the AT-802U at over two thousand kilograms, lending credibility to Air Tractor’s claims of a 10-hour endurance. The reason for this large fuel load is because of its background as a Crop Duster or Fire Fighting aircraft wherein it has large liquid containers between the engine firewall and the cockpit and also under the belly which has been converted to carry fuel instead on the AT-802U. And even with a full internal fuel load, the AT-802U can still carry well over a thousand kilogram of external payload.
+++ The AT-802U carries so much fuel that it could actually trade off some of that fuel along with endurance and range so it can carry more external payload as needed. For example, if the AT-802U matches the fuel factor of the A-29B which is at 0.10, it will be able to carry 2,714 kg of payload, or 43% more than the A-29B.
‘Avionics and Weapons’
Although these aircraft are propeller-driven and thus may seem “obsolete” to some, they actually have some of the most advanced Avionics available in the world today, ranging from Heads Up Displays (HUDs), Hand On Throttle And Stick (HOTAS) controls, “Glass” cockpits, etc. Here is a list of the Avionics Suite and weapons of both aircraft:
– WEAPONS: The advantage goes to the Super Tucano’s two internal guns despite the fact the AT-802U has six more additional hardpoints.
– AVIONICS: The A-29B has the advantage of having a Missile/Radar Warning Receiver (M/RWR) and Counter Measure Dispenser System (CMDS) built in.
+++ Although the AT-802U has a LOT more hardpoints than the Super Tucano, the A-29B’s internal guns have less drag than the comparable gun pods that the AT-802U will have to carry.
+++ The Iomax Archangel is confirmed to have M/RWR and CMDS, but AT-802U offers it only as an “option”.8 At any rate, the addition of these two systems will result in a heavier empty weight which will mean less fuel and external payload for the aircraft.
Unlike with the AT-6B, Embraer did not put up a webpage dedicated to showing the superior features of the A-29B over the AT-802U, perhaps because they don’t consider the AT-802U as a major competitor. At any rate, one clear advantage that the A-29B has over the AT-802U is cockpit visibility. The A-29B uses a clear bubble canopy, while the At-802U uses a canopy lined heavily with steel frames and thus severely limiting visibility.
Another issue is that the cockpit is set way back in the body so that long, big nose housing the engine and fuel limits the visibility of the ground in front of the pilot. Even worst is that it uses the conventional, tail-dragger type of landing gear which keeps the nose of the aircraft high when it is taxiing on the ground, reducing frontal visibility even further and makes it a little bit more difficult for the pilot to see where he is going, which could be a challenge especially for novice pilots.
While the AT-802U’s steel-lined cockpit reduces visibility, it also allows the cockpit to use ballistic glass for added protection against enemy fire, hence the AT-802U traded off visibility for armor protection. However, this is somewhat offset by the fact that it doesn’t have ejection seats, so the pilots will have to manually crawl out of the plane to bail out, or rely on the air bags, secure seat belts and a sturdy landing gear when ditching (i.e. crash landing) the aircraft.
Another issue is the fact that the AT-802U has an airconditioned but NOT a pressurized cockpit, limiting its operating altitude to around 3,800 m. The Super Tucano with its pressurized cockpit can operate all the way up to its service ceiling of 10,600 m. Only a minor issue as these aircraft are expected to operate close to the ground anyway, MOST of the time, but not ALL of the time. In SOME situations, for example, like when it would be SAFER against ground fire to drop PGMs from beyond 3,800 m altitude, that option is not available with the Air Tractor.
Summarizing the advantages for the AT-802U Air Tractor:
– Can travel twice as far or carry more payload
– Has a lot more endurance or time on station
– Has a lot more hardpoints
– Has better ballistic protection
– Better rough field performance
– Potentially more maneuverable
– Reportedly has much less Operating Cost
– Reportedly has lower price
Summarizing the advantages for the A-29B Super Tucano:
– Can carry more payload if both aircraft are at full internal fuel
– Is much faster making it less vulnerable to ground fire
– Can reach combat areas faster
– Imparts more Kinetic Energy during launch allowing some weapons to travel further
– Has better vertical performance
– Has better Cockpit visibility
– Has Ejection Seats
– Has M/RWR and CMDS
– Smaller aircraft physically, and thus a smaller target
– Has a Pressurized cockpit, and thus a much higher maximum operating altitude
Designs are always a compromise, and with the AT-802U it is obvious where the compromises are in terms of performance: It sacrificed speed and vertical performance for potential maneuverability and superior endurance, range, or payload. Its slow speed coupled with its lack of warning and counter measure system means it is ideal only against “low-threat” opponents, like Insurgents or Separatists firing their rifles into the sky.
But against an opponent with Surface to Air Missiles and/or radar-guided cannons, even if M/RWR and CMDS are fitted in, the AT-802U’s slow speed will still make it more vulnerable to enemy fire. Also don’t forget that the largest agricultural aircraft in the world would also make for a relatively larger target.
It is a DURABLE target with all that ballistic protection, but an aircraft can only take so much punishment after which it will start falling out of the sky. IMHO, the AT-802U is better for Law Enforcement or Special Mission/Forces use (like what UAE is using them for) rather than an attack aircraft, and it will definitely excel in those roles. Meanwhile, for the PAF, IMHO the A-29B Super Tucano will be better as it will be more survivable against “external threats”. Yes, I meant China.
- WING LOADING = is the amount of weight the wing supports during flight, and is expressed in weight per area, or in the metric system, kg/m^2. This is computed by: (Wing Area divided by Weight).
POWER TO WEIGHT RATIO = means how much power the aircraft has compared to its weight, and is expressed by a simple number. This is computed by: (The maximum power of the aircraft’s engine divided by weight).
INTERNAL FUEL FRACTION = is the weight of the internal fuel the aircraft compared to its maximum take-off weight, and is expressed by a simple number. Formula used is: (Maximum internal fuel capacity divided by maximum take off weight). http://en.wikipedia.org/wiki/Fuel_fraction
Embraer EMB 314 Super Tucano,
Air Tractor Production Milestones,
Air Tractor AT-802,
Middle East Embraces New Iomax Aircraft,
Iomax Archangel specifications,
LAS in, LAS out: Counter-Insurgency Planes for the USA and its Allies,