Tag Archives: fighter generations

Guess what’s worse than a flameout on take off? A flameout on catapult launch from an aircraft carrier

A quite embarrassing episode marked the end of MAKS 2011 air show on Aug. 21, at Ramenskoye air base, near Moscow. The Sukhoi PAK-FA/T-50, Russia’s 5th generation fighter plane, was forced to abort take off after suffering a flameout in the right-hand Saturn engine.

As below footage shows, the T-50-2, the second prototype of the stealth fighter (52 Blue), aborts its take off roll  after bursts of flames erupted from the engine.

Deploying the airbrakes and the two drag chutes after reaching a speed of around 60 MPH, Sukhoi’s test pilot was able to halt the aircraft well before the end of the runway.

If the PAK-FA flameout in front of some 200.000 spectators had only a negative impact on Sukhoi’s reputation, similar engine failures can be quite thrilling if they occur to fully loaded planes in dangerous phases of a flight: departure, initial climb, landing.

I took the top picture in the Indian Ocean aboard USS Nimitz (CVN-68) on Oct. 19, 2009. An F-18C (BuNo 165205 Modex 405) belonging to the VFA-86 “Sidewinders” experiences a compressor stall during the catapult launch from CAT number 4. The aircraft is fully loaded with fuel and weapons, and it is taking off to perform an on-call CAS in support of Operation Enduring Freedom in Afghanistan.

Fortunately, the aircraft took off in spite of the loud bang and flames coming out from the port engine exhaust that in the second image seems to be operating without the afterburner.

Here’s the entire sequence of the launch showing the single engine departure.

The compressor surge is a particular kind of compressor stall that occurs when the hot vapour generated by the aircraft carrier’s catapult is ingested by the aircraft air intake thus creating a breakdown in compression resulting in a the compressor’s inability to absorb the momentary disturbance and to continue pushing the air against the already-compressed air behind it. As a consequence, there’s a momentary reversal of air flow and a violent expulsion of previously compressed air out through the engine intake producing some loud bangs from the engine and “back fires”.

The compressor will usually recover to normal flow once the engine pressure ratio reduces to a level at which the compressor is capable of sustaining stable airflow. Some engines have automatic recover functions even if pilots experiencing the surge can be compelled to act on the throttle or, in some cases, relight the engine.

Compressor surges are frequent on U.S. aircraft carriers. Unlike the T-50, that could precautionally abort its take off, carrier air wing airplanes can’t stop their run once it’s started. Fortunately, F-18s are used to take off even if an engine is temporarily unserviceable: this shows once again how rusty Legacy Hornet are sometime tougher than some 4+ or 5th generation “colleagues”.

I don’t know if a PAK-FA would be able to take off after experiencing a compressor surge aboard an aircraft carrier but I know for sure the F-35C (that, along with the other variants has returned to fly last week, after being grounded for an IPP failure on Aug. 3) won’t: it’s an easy-to-fly, single-pilot, 5th generation fighter jet. With a single engine.

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Fighter generations comparison chart

The appearance of the new J-20 (unofficially dubbed “Black Eagle”) raised many questions about the Chinese stealth fighter. Some experts think it will be more capable than the F-22; others (and I’m among these ones) think that the real problem for the US with the J-20 is not with the aircraft’s performance, equipment and capabilities (even if the US legacy fighters were designed 20 years earlier than current Chinese or Russian fighters of the same “class”); the problem is that China will probably build thousands of them.

Anyway, comparing the US and Chinese fighters, everybody referred to “fifth generation planes” bringing once again the concept of “fighter generation” under the spotlight.

Generations are a common way to classify jet fighters. Often, generations have been “assigned” to fighters in accordance with the timeframes encompassing the peak period of service entry for such aircraft.

The best definition I’ve found so far of fighter generations is the one contained in an article published in 2009 by Air Force Magazine, that proposes a generations breakdown based on capabilities:

Generation 1: Jet propulsion

Generation 2: Swept wings; range-only radar; infrared missiles

Generation 3: Supersonic speed; pulse radar; able to shoot at targets beyond visual range.

Generation 4: Pulse-doppler radar; high maneuverability; look-down, shoot-down missiles.

Generation 4+: High agility; sensor fusion; reduced signatures.

Generation 4++: Active electronically scanned arrays; continued reduced signatures or some “active” (waveform canceling) stealth; some supercruise.

Generation 5: All-aspect stealth with internal weapons, extreme agility, full-sensor fusion, integrated avionics, some or full supercruise.

Potential Generation 6: extreme stealth; efficient in all flight regimes (subsonic to multi-Mach); possible “morphing” capability; smart skins; highly networked; extremely sensitive sensors; optionally manned; directed energy weapons.

In order to give the readers a rough idea of the type of aircraft belonging to each generation based on the above breakdown I’ve prepared the following table with the help of Tom Cooper / ACIG.org and Ugo Crisponi / Aviatiographic.com, who provided the profiles. It’s not meant to show all the aircraft theoretically belonging to a generation and includes only the profiles available at the time of writing…

As I’ve already said on Twitter, what such a table should let you understand at a glance is that capabilities and appearance are inversely proportional: former generations aircraft look much better than more modern fighters…..

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