Monday, October 27, 2014

When your airplane (r)ejects you . . .

It seems the Indian Air Force recently experienced a very puzzling accident involving one of its Sukhoi Su-30MKI aircraft when the ejection seats launched the two-man crew into thin air without so much as a "By your leave".

India has grounded its entire Sukhoi-30 fleet after a recent crash because it doesn’t want to put its pilots in harm’s way.

. . .

With the IAF operating close to 200 twin-engine Su-30s, the grounded planes represent almost a third of the country’s fighter fleet. India is due to get 72 more of these planes, each worth over Rs. 200 crore [more than US $40 million].

An IAF official said safety checks with “special focus on ejection seats” were being conducted and flight operations would resume only after each plane was cleared. A highly-placed source said the pilots of the plane that crashed on October 14 near Pune had reported “automatic seat ejection.” One of the two pilots was involved in a previous Su-30 crash too.

Five Su-30 fighters have crashed during the last five years, setting off alarm bells in the IAF. The Su-30 fleet has been grounded at least twice in the past.

Former IAF chief Air Chief Marshal Fali Major told HT, “A fleet is grounded when you have no clue as to what brought the plane down. It’s serious.”

There's more at the link.  The aircraft doesn't look very badly damaged in the picture - it was on final approach, so it didn't have much time to go further out of control - but looking at the ruptured fuselage below the cockpit area, I have to doubt whether it'll fly again.

There are a number of puzzling elements here.  How and why did the ejection seats fire uncommanded?  Their circuits are very carefully designed to avoid that, even if they sustain battle damage.  Also, I have to assume they were on a joint circuit, so that if one seat fired the other would automatically do so as well.  If not, why did both fire rather than just one?  Finally, why did they fire on final approach, when the aircraft's (presumably) not involved in high-speed, high-g maneuvers that stress the airframe and systems?

I can't imagine what it must have been like for the aircrew.  One moment they're flying along, preparing to land, hands on the controls, busy with their checklists . . . and next moment they're in mid-air, wondering what the hell happened and how they got there!



Anonymous said...

Operation of complex machinery is very cultural. Boeing got in trouble for publishing that fact years ago.

Recent past the IAF had an absolutely atrocious mishap rate on M21 aircraft. They blamed it on old technology and russian design. Hmmm. Now they have new tech russian design and they are still doing the lawn-dart thing. You dont, never mind.

Dual seat aircraft generally (although I have no time in Su30)a selectable ejection sequence. Each seat independently or sequenced ejection. Much can go wrong with these systems and we have had our share of egress-related mishaps.

Safe? Eeeeeze not safe! Eeeeze sitting on top of explosives.

Anonymous said...

From the looks of the paint on the tail... their maintenance program is a little bit on the shade tree side. Although that being said, I have seen an F-18 land at our local college airport and there were chunks of main-gear tread on both mains missing to the point you could see the ply-cords in the tires.

Paul said...

Maybe ground proximity sensor? thought the air craft was going to crash and sent the pilots off to survive.

Not that I am an aerospace engineer or anything.

David said...

One does not eject from Russian aircraft...Russian aircraft ejects you!

Old NFO said...

Question is were the ejections sequential or simultaneous? And a bunch more... Not enough info to even have an idea. Anon is also probably as correct as anyone is...

Anonymous said...

Paul, if the airplane is in a landing configuration (landing gear extended and/or flaps down) then the GPWS is locked out to prevent annoying distractions on final approach.

Peter, I doubt that much of the airplane is salvageable. I know that Bombardier refuses to have anything to do with any part of a crashed airplane; it is all scrap according to them. GE will put out a service bulletin listing any engines involved in an 'abnormal occurrence' and list every part of the engines by p/n and s/n telling everyone the parts are not airworthy.

Incidentally, my buddy who wrenched on Hawker Hunters in the '50s tells me that he was taught that ejection seats at that time had killed more people than they had saved due to accidental firing on the ground. Without airflow to blow it clear the crew be fired into the canopy and mechanics were fired into hangar ceilings.


JohninMd.(HELP?!??) said...

Also, I believe two seated jets are set so the back seater goes first by a small margin, so as not to get fried by the front seat's rocket.