Apart from being able to fly faster, and thus being able to reach to an operating atitude sooner, what other advantage would a turbofan powered AEW platform have over a turboprop powered platform? Would a turbofan AEW platform, on account of being able to fly higher, have better radar coverage?
The merits of a turbofan powered platform over a turboprop one for AEW
- Thread starter STURM
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I'd expect turbofans to be much more efficient at the higher altitudes that AEW aircraft usually fly.
Also, the power generation from turbofans should be more than from a comparable turboprop.
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You're probably right but what I'm more curious about is whether the radar can see further if the platform was flying at a higher altitude. Apart from wanting an aircraft with a faster dash speed, with more range and endurance, surely the reason many have gone for a jet/turbofan platform is the higher service ceiling ?
Commuter turboprops routinely cruise at 25000 feet. At that height the absolute horizon is 310km which is near the capabilities of most AEW radars anyway (IIRC the E-3 has a max range of around 420km).
So while there shouldn't be any real difference in radar performance between turboprops and jets I think customers prefers jets mainly because
- The propellor blades on a 'prop cause a small but noticable effect on radar performance, and
- There a lot more suitable jet platforms than comparable turboprops
Don't the Swedish have a turbo prop for their AEW aircraft I know it is smaller than allot of AEW aircraft maybe its the size over a certain size turbo fan engines may just be a lot more efficient or powerful the C 130 is turbo prop but all bigger cargo aircraft such as the C17 or the Galaxy were all turbo fans You see the same in commercial planes small the popular city hoppers seem to be turbo prop but as soon as there are more than a 100 passengers they are nearly all turbo fan.
Humming Drone
New Member
Most AEW aircraft are based on modified civilian airframes. It has to be large enough to support the equipment and crew, etc. Larger airliners use turbofans. Efficient, less noise, less vibration.
Ananda
The Bunker Group
Sturm, I believe that size, range, of present turbofan platform mitigate the economics advantage of turboprop platform this days. lockheed try to sell C-130J platform as possible alternative to B 737 platform for some customers that want to have slightly less capable platform but offered near simmilarity on the amount of electronics that can be installed.
However C 130J is not what you can called cheap, so does big turboprop platform like Airbus one. The questions can be more to be ask is what the advantage of small turbofan platform like gulfstream compared to say SAAB or C-295. However Gulfstream do if not mistaken offered bigger range compared to smaller size turbprop.
In short I do believe that range of present turbofan platform more matter compared to ceiling hights.
However C 130J is not what you can called cheap, so does big turboprop platform like Airbus one. The questions can be more to be ask is what the advantage of small turbofan platform like gulfstream compared to say SAAB or C-295. However Gulfstream do if not mistaken offered bigger range compared to smaller size turbprop.
In short I do believe that range of present turbofan platform more matter compared to ceiling hights.
Todjaeger
Potstirrer
From my perspective, there is not much difference in fan vs. prop for AEW. It has everything to do with the type of radar aboard the AEW aircraft, and then what that radar requires from the aircraft platform itself.
Take two of the most numerous AEW aircraft types, the E-2 Hawkeye (prop) and the E-3 Sentry (fan). The primary users for these are the USN and USAF respectively.
IIRC the cruising altitude for the Hawkeye is 40,000 ft, about 1,000 ft higher than for the Sentry. In both cases, roto-domes are used, projecting the radar signals above the wings and therefore away from the engines. This needs to occur because the materials of the wing would reflect that signal, and depending on signal output, the radar could negatively impact the safe operation of the aircraft.
This has been part of what has delayed the appearance of the (E-7 IIRC?) Wedgetail AEW&C in RAAF service. The power output from the MESA can impact commands from the cockpit, and therefore the steerable beams need to be programmed so as to prevent them from coming in contact with the wings, etc.
From my perspective, what should really matter is how appropriate an aircraft is in terms of altitude, power generation and loiter time, relative to the radar/comms systems used for AEW.
If the aircraft can fly very high and therefore has a long radar horizon, but the radar system itself is quite short-ranged before the signal attenuates to uselessness, then the aircraft is likely 'overkill'. OTOH, it the radar system can handle long-ranged signalling, but the aircraft can only meet 70% of the power generation or cooling requirements, then the aircraft is likely insufficient.
Similarly, if the aircraft has the 'right' altitude and power capabilities, but can only stay on station for 30 minutes... It would still be the wrong aircraft.
-Cheers
Take two of the most numerous AEW aircraft types, the E-2 Hawkeye (prop) and the E-3 Sentry (fan). The primary users for these are the USN and USAF respectively.
IIRC the cruising altitude for the Hawkeye is 40,000 ft, about 1,000 ft higher than for the Sentry. In both cases, roto-domes are used, projecting the radar signals above the wings and therefore away from the engines. This needs to occur because the materials of the wing would reflect that signal, and depending on signal output, the radar could negatively impact the safe operation of the aircraft.
This has been part of what has delayed the appearance of the (E-7 IIRC?) Wedgetail AEW&C in RAAF service. The power output from the MESA can impact commands from the cockpit, and therefore the steerable beams need to be programmed so as to prevent them from coming in contact with the wings, etc.
From my perspective, what should really matter is how appropriate an aircraft is in terms of altitude, power generation and loiter time, relative to the radar/comms systems used for AEW.
If the aircraft can fly very high and therefore has a long radar horizon, but the radar system itself is quite short-ranged before the signal attenuates to uselessness, then the aircraft is likely 'overkill'. OTOH, it the radar system can handle long-ranged signalling, but the aircraft can only meet 70% of the power generation or cooling requirements, then the aircraft is likely insufficient.
Similarly, if the aircraft has the 'right' altitude and power capabilities, but can only stay on station for 30 minutes... It would still be the wrong aircraft.
-Cheers
Wiki Has 34k as a max altitude - I know there are better sources than wiki though...
Todjaeger
Potstirrer
IIRC that 40,000 ft figure I had gotten from Global Security some time ago. When I check back now, the altitude for the E-2C is not listed. Reading through the notes on it though, a service ceiling of 37,000 ft is mentioned for the E-2C Group I aircraft, which debuted in 1988 with an uprated engine.
I might have had the figure wrong, and it might not have been the cruising but instead the max service ceiling.
-Cheers