ejections system on choppers

With Mode 3, say if Mode 2 conditions are never met? Then you'd be pretty much screwed, right? Would it be possible for the pilot to take manual control of the system, or is that just pointles because he/she would be too disorientated from the spinning and whatnot?

btw, HOKUM kicks ass.

Originally posted by RedMatt
Helo's are inherently safer than aircraft however, because the rotors can be allowed to freewheel in the wind, acting like a parachute and allowing you to return to the ground in a (somewhat) safe maner.

not necessarily. if youre in a hover, you have no momentum to get the rotors going fast enough for an autorotation. basically, you just fall out of the sky. if you are low and slow, same thing.

No, snafu7700, autorotation does not rely on forward momentum to generate rotor rpms. Rather, the pilot angles the actual rotors so that as the helicopter falls vertically the air causes the rotors to turn very fast. When the helo nears the ground, the pilot adjusts the rotor angle once more so that they generate maximum lift and the speed of the rotors forces air down, as would normal rotors with an engine turning them.

Of course, this cannot be done at low altitudes or if you have no rotors (??), but yeah.

It also takes a lot of skill to get the timing right. If you lose your nerve and yank the collective too soon, the machine will stop briefly but will be too high.

[edit on 7/8/2006 by watch_the_rocks]

ummm, you might want to look that one up. think you'll find that it's impossible to autorotate from a hover.

Aherm.

Although helicopters will autorotate at zero airspeed and even at negative airspeed, normally the pilot will want to hold between 60-70 knots of airspeed during the glide.

Wiki

Forward speed is used to keep the helicopter stable, and to get to a landing site.
But it is not necessary! If you were at a lowish altitude, you would want to go straight down as much as possible to maximise the amount of air flowing through the rotor disk to get the rotors spinning as fast as possible. If you were over a city or dense forest, then you'd damn well want to go forward afap.

Originally posted by watch_the_rocks
Forward speed is used to keep the helicopter stable, and to get to a landing site.
But it is not necessary! If you were at a lowish altitude, you would want to go straight down as much as possible to maximise the amount of air flowing through the rotor disk to get the rotors spinning as fast as possible. If you were over a city or dense forest, then you'd damn well want to go forward afap.

Actually forward airspeed will help to spin the rotors providing power for the flare during autorotation. Another benefit of forward airspeed is that it helps to keep the helo from spinning out of control due to the lack of torque from the tailrotor.

Yeah yeah, sin't that what I said?

Choppers don't have jeaction systems. The rotars would chop them up like a salad.

Instead, helicopters have something called Autorotation! If they're going down, they can mecanically pitch the rotar blades to catch the air and spin on their own. This slows down the rate of decent just enought to allow the crew to survive impact, if it works correctly!

Tim

Actually there are at least two variables inherent to the question of helicopter ejection systems.

First, getting to a point in the envelope where they are most capable of reacting in time to almost any departure from controlled flight with an auxilliary recovery system.

Second, reducing the number of times where such a system is required as a function of deliberate envelope point or environmental/threat hazarding.

Fortunately, especially in low intensity conflicts which are just about the only area where combat helos still have any true utility, the answer to both questions is basic:

Standoff And Altitude.

If you are at height, you don't have a terrain or attitude modifier which effects TIME necessary to sever the rotors explosively, remove the cabin roof or canopy and get the seats going up the rails on a 2-then-1 basis typical for most attack helos before impact with the ground or some obstacle (or an unbalanced rotor disk striking the tail or cockpit and further destabilizing the craft. Or a wingman being able to leave the proximal danger zone as the EBolts go off. Among many other 'what if' problems).

Furthermore, trashfire (low caliber AAA and unguided rockets) are much more difficult to aim because there is less angular rate lead reference even as the projectile trajectories are more effected by ballistic drop and TOF. You are of course more vulnerable to guided threats but these are generally better dealt with by active defenses than maneuver or masking where randomly encountered (TOF problem again). And the higher you are, the longer the automated (MLDS) defenses have to see the threat leave the clutter and do something about it with expendables and jamming.

There is a further list of 'enablers' that probably could be applied to further this goal:

1. Compound Propulsion and Lift Augments.
If you have a separate propulsion system you don't need to tilt the disk or the airframe as dynamically to regain speed when maneuvering in close proximity with any terrain hazard. If you have wings, you don't have to rely on the disk for sole-source lift. Theoretically, you can even further isolate or cross-shaft render redundant the drive trains to ensure that any given single point failure doesn't compromise BOTH forward propulsive and main rotor drive empowerment.

2. Fuselage Rocket Boosting or Pararecovery.
If you cannot clear the terrain or the aircraft in time, the only remaining choice is to make the airframe do it for you. While this would nominally require a rather large explosive motor inside the fuselage (posing it's own risk) the notion of retrorockets and a rocket-drogue canopy might at least combine to stabilize the orientation of the aircraft while giving it a fairly soft landing (within the fps limits of the crash safe seats anyway).

3. Fuselage Air Bags.
Both as cockpit immobilizers to the pilots (protecting them from shattered canopy fragments and collapsing instrument/sighting systems). And as direct impact and possibly floatation rated external impact attenuators.

4. Mini-Drones and LOAL Powered Attack Systems.
The inherent cost value of a helicopter is such that, today, it is LESS sacrificable than say an MBT. As such you are wiser sending a bullet than the airframe to investigate particularly an intra-urban fight. Because the concentration of enemy and collaterals is so dense that you cannot choose sheep or goats but must engage the lot, often for /miles/ in any direction or depth. If said drone also carries a cassette of vertical topattack grenades which have frag/HEAT/D/A modes then so much the better. But there is ABSOLUTELY NO REASON to pay for a 2 million dollar set of high fidelity sights (literally made to the same levels of clean-room quality that a satellite is) only to put it nose-first into a hail of bullets costing on the order of a quarter. Not when you can look at the /back side/ of a target building or terrain feature, by sending a 500 dollar camcorder equivalent sensor on a direct overflight in a drone. Piss Poor weapons systems are in fact the principle shortcoming in modern attack helicopters today.

5. Replacement Of The Rotors.
I know it's an obvious statement to make but particularly with the arrival of multipost auxilliary propulsion systems able to generate balanced lift twice or more the individual rating of the individual cruise engine without L+LC cycle reliability and plumbing complexities; it's truly time to consider whether the multiple mechanical articulations of a conventional (engine + transmission) helicopter are required or wise. At least in the military, this decision is, I'm convinced, as much based on doctrinal 'tradition' (cough, Key West!, cough, cough) as any real technical superiority inherent to the penny farthing rotary wing system.

CONCLUSION:
If you can't leave a combat aircraft, you'd bloody well better reduce the number and frequency of datapoints wherein _Highest Risk Exposure Employment_ doctrine AND _Most Dangerous Aero-Mechanical Failure Point_ (coming off or into the cushion at hover and high rpm) engineering limitiations to a given configuration come together.

Because, in a helicopter especially, that airframe is effectively both the lifeboat and (the rotors) the circling sharks and any terrain or obstacle feature encountered at high speed represents a coral reef capable of ripping the bottom out of the hull and bringing you into the teeth of your own propulsion system.


KPl.

I remember when I saw a james Bond where he manged to escape through a chopper ejection.

Anybody remember the movie?

What a coincidence....I saw a commercial for a helicopter ejection system last night on telly....

"It slices, it dices, it julliene's fries! Make Cole Slaw (out of a pilot) in seconds flat! It's the amazing new Pilot-o-matic automatic slicer!!"

Or something like that...