EGRESS Failure

Military aircraft accidents/mishaps.
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interlogika

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Unread post03 May 2011, 04:45

Hello guys,
have a question for the Egress folks.

How likely is it that an activated seat on a fighter/trainer (i.e. a seat upon which a crew member begins the ejection sequence by pulling handle), would simply not fire properly or fire only to remove canopy but not eject seat?

Is this stuff of novels, or can it actually happen on the older seats (T-38's and company)?

cheers!
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Roscoe

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Unread post03 May 2011, 05:57

With all the inspection cycles, seat failures are almost nonexistent, so long as you eject anywhere close to the ejection envelope
Roscoe

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launcherman

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Unread post03 May 2011, 07:16

Could have pulled the canopy eject handle...
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interlogika

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Unread post05 May 2011, 02:25

Hey guys, thanks for the feedback.

One question though: what would pulling the canopy ejection handle do if the seat misfired?

Also, does the ejection envelope affect the ejection of the seat or only the survivability of such ejection?

cheers!
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launcherman

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Unread post05 May 2011, 06:36

That was the only thing I could think of. With the reliability of the seat, I don't see it NOT leaving once the handles pulled.
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rockstar08

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Unread post01 Dec 2011, 10:14

interlogika wrote:Hello guys,
have a question for the Egress folks.

How likely is it that an activated seat on a fighter/trainer (i.e. a seat upon which a crew member begins the ejection sequence by pulling handle), would simply not fire properly or fire only to remove canopy but not eject seat?

Is this stuff of novels, or can it actually happen on the older seats (T-38's and company)?

cheers!


Sorry for the late reply, I didn't realize there are no Egress people on here.

The answer to your question is, it's the stuff of novels. I've never once heard of a failed ejection due to an issue with the seat or the ejection system. Not once. Only ridiculous stories from 25 years ago that somebody heard from somebody else who heard it from someone else.

- Decade and still going of Egress experience on active duty.
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razamanaz

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Unread post21 Mar 2012, 03:29

Ejection seat malfunctions are extremely rare but not impossible as evident by the fact the subject is addressed in the flight manual of any aircraft equipped with an ejection seat. Early ejection seats (circa 1940's) were built by the same companies manufacturing the aircraft they were to be used for and thus research/development/testing/production remained dependent upon the limited technology available as well as budgetary constraints. Some of these early ejection seats utilized little more than an ejection handle connected to a primer which fired the seat's telescoping catapult. As there were no redundant back-ups or automatic sequencing systems, a pilot pretty much pulled his ejection handle and hoped for the best. After entering the supersonic age, companies such as Martin-Baker of England began specializing in ejection seats which resulted in greatly increased reliability. Modern ejection seats such as the ACES-II, Martin-Baker Mk-16 and Zvesda K-36 are 99.999% failsafe with the operating time from pulling the ejection handle to safely hanging below a fully inflated parachute reduced to just 3 seconds.

Escape system advancements already explored include articulating seats which can be reclined as much as 55 degrees during flight for increased comfort/G-force tolerance and automatically repositioned upright for ejection within 30 milliseconds of pulling the ejection handle... such a seat was designed for the YF-22 prototype using a modified ACES-II seat. Vertical-seeking self-righting seats have been tested which provide safe ejection while inverted as low as 50 feet AGL. An automatic ejection system was used by the former Soviet Union's Yak-38 VTOL fighter to eject the pilot if one of the vertical thrust engines failed during ascent/descent/hover. Russia's Ka-50 helicopter is equipped with a Zvesda K-37 ejection seat which fires after the main rotor blades and canopy are jettisoned.

In the end, even the most advanced ejection seat technology will remain only as reliable as the egress technicians who maintain/inspect them and the air crews who must make the decision to pull the ejection handle.

(31 years in the egress arena)
Last edited by razamanaz on 22 Mar 2012, 20:20, edited 4 times in total.
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TC

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Unread post22 Mar 2012, 12:56

Pulling handles outside of the seat's envelope will still punch you out. The seat doesn't know or care whether the airspeed and/or altitude is within certain perameters. All it knows, is that you've pulled handles, so it's time to go. That said, ejecting outside of the seat's envelope does not guarantee an unsuccessful and/or fatal ejection. It simply means you are doing something that the seat was not designed to do. However, if it's time to go, it's time to go. If it comes down to ejecting out of the envelope or turning into a smoking hole in the ground, I'm fairly certain that it's clear what choice folks will make. Neither one is the optimal choice...HOWEVER, one choice definitely trumps the other!
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razamanaz

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Unread post22 Mar 2012, 18:48

Just to clarify the term "ejection envelope" for anyone who may be unfamiliar with egress systems... it simply means the minimum and maximum operating parameters for which an ejection seat is designed and rated to provide safe escape. Most modern ejection seats are rated "zero-zero" which means they can be used to escape from an aircraft with zero airspeed and zero altitude (e.g. aircraft sitting on a ramp or runway). Many early ejection seats required a minimum airspeed (e.g. 90 knots) in order to provide sufficient airflow to aerodynamically remove canopies or escape hatches (such as the B-52's upward escape hatches). A minimum airspeed was also needed to assure full parachute deployment and inflation when ejecting at low level. Because early ejection seats were less powerful due to the lack of rockets, a minimum ejection altitude (e.g. 250 feet AGL) was frequently required to allow time for crew member/seat separation and parachute deployment. Seats that eject downward such as the B-52 navigator and radar-navigator of course also have minimum ejection altitudes to allow time for crew member/seat separation and parachute deployment. If time allows during low level ejections, B-52 pilots may try to bank or zoom the aircraft just to give the navigator and radar navigator a better chance for survival by offsetting their straight downward ejection trajectory. Ejection seats also have a maximum airspeed rating due to the windblast effect which can cause limb flailing injuries, failure (blowout) of the seat's drogue/stabilization chute, and collision with the aircraft structure (notably the vertical stablizer). Maximum ejection altitudes normally fall within the aircraft's maximum operating ceiling... since modern ejection seats include self-contained emergency oxygen systems, the biggest danger posed by high altitude ejection is frigid air temperatures until the seat falls to a lower/warmer altitude (e.g. 15,000 feet AGL) and automatically releases the crew member for parachute deployment. Other factors affecting the ejection envelope include aircraft bank angle, pitch angle and sink rate. Ejection seats also have minimum/maximum crew member weight parameters in order to maintain the seat's center of mass/center of gravity during ejection.

Some aircraft were equipped with enclosed escape systems to better protect crew members during ejection at supersonic speeds. The B-58 and B-70 used individual escape capsules for each crew member. The F-111 and B-1A were fitted with escape modules by which the entire cockpit section ejected from the aircraft. The SR-71 was equipped with Lockheed ejection seats because of limited cockpit space and the fact crew members were well-protected by astronaut-style Clark pressure suits if they had to eject at high airspeeds. An F-111 type escape module was initially proposed for the space shuttle but was rejected due to complexity, cost and weight... such an escape system may have saved the crew of Challenger (especially since the entire cockpit section was completely separated from the shuttle during the explosion) and possibly the crew of Columbia as well. Shuttles Enterprise and Columbia were initially fitted with two Lockheed ejection seats similar to those used in U-2 aircraft but the seats were removed after Columbia's fourth mission to reduce weight and accommodate additional crew members. While these seats were rated for use up to 100,000 feet, they were useless while sitting vertically on the launch pad or during the hypersonic speeds encountered with launch and re-entry.
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razamanaz

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Unread post23 Mar 2012, 04:00

razamanaz wrote:Zvesda K-36... Zvesda K-37...


Not that it matters but the correct spelling for Russian ejection seats in my earlier post is Zvezda not Zvesda
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razamanaz

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Unread post23 Mar 2012, 04:47

TC wrote:Pulling handles outside of the seat's envelope will still punch you out. The seat doesn't know or care whether the airspeed and/or altitude is within certain perameters. All it knows, is that you've pulled handles, so it's time to go. That said, ejecting outside of the seat's envelope does not guarantee an unsuccessful and/or fatal ejection. It simply means you are doing something that the seat was not designed to do. However, if it's time to go, it's time to go. If it comes down to ejecting out of the envelope or turning into a smoking hole in the ground, I'm fairly certain that it's clear what choice folks will make. Neither one is the optimal choice...HOWEVER, one choice definitely trumps the other!



A classic example of intentionally ejecting outside the envelope as the lesser of two evils involved the F-104 Starfighter. Design engineers claimed available off-the-shelf ejection seats of the 1950's era didn't possess adequate thrust to clear the vertical stab when bailing out at high airspeeds. Their solution was to equip the jets with a downward egress system even though history had proven a large percentage of ejections occurred during take-offs and landings. Pilots of course found little humor in the idea of being blasted into the ground and knew their only hope of surviving a low level bailout would be to try to roll their jet inverted and eject upside down even though doing so exceeded the capabilities of the seat. After 21 F-104 pilots were killed during low level ejections, the Air Force and engineers finally wised up and decided a downward egress system wasn't such a bright idea after all. As a result, all F-104's were retrofitted with an upward ejection system using the most powerful seat available... unfortunately, humans are creatures of habit and two more pilots were killed when they rolled their jets inverted before ejecting at low altitude with the new upward egress systems.

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