We are as usual, forced to confront ourselves with the question of why it is that we need to know this? Rotary wing aviation is becoming more and more prevalent as a choice for such things as sightseeing, survey, surveillance and the ubiquitous EMS service.
It is therefore likely that you, dear reader, are going to find yourself jolting around in the back of one of these aircraft at some point in during your existence. This node is aimed at extending that existence (if possible.)
Why here and not in the middle of How to survive an aircraft mishap? Surviving inside of a fixed wing aircraft mishap is something that you are likely to do, whereas surviving inside of a helicopter is something that depends mostly on the skill of the pilot and luck.
There are also some aspects of rotary wing aviation survival that require some specific discussion. For instance, getting out of a helicopter after it has hit the water is an entirely different ball of wax from hitting the water in a conventional fixed wing aircraft.
One of the primary differences is that if you were to hit the water in a conventional fixed wing aircraft you are probably going to float for a little while (between fifteen seconds and five minutes depending on how well the wings are sealed and how much damage the airframe sustained during the crash sequence.)
Helicopters on the other hand, do not float. They flip over (invert) and then they sink. They do this far more quickly than you would think. The emergency floation (read: air bags attached to the skids) that they install on some aircraft are great looking devices, however this is all they are and not likely to do you a whole fat lot of good in a crash.
As a matter of fact, flotation bags used to be standard equipment on the RAN-70 (Australia,) S-70 (Japan,) SH-60B and SH-60F Seahawk (United States.) That is they were until the engineers figured out that in a water landing the flotation bags actually held the doors shut which prevented the pilots from exiting the aircraft. Water landings, how to simulate them and what to do in the event of a water landing will be tackled below in How to Survive Underwater Egress Situations.
Getting Yo’ Ass Out Da Billion Dollar Blender:
As usual, some things you need to remember that will be helpful when you find yourself on the wrong end of the stick.
-Face it, you’re screwed.
Not to be blunt, but you are up the proverbial creek here. You’re in a helicopter that is crashing, and this is not a healthy situation to get yourself into. For starters, helicopters have problems disintegrating while in mid-air and additionally they tend to turn themselves into easy to clean up balls once they do hit the ground. This is due to the amount of torque generated by the rotor system, and is not something that you can avoid.
-If possible, sit in the cabin as close to the rear wall as possible.
While sitting inside of a helicopter, the main gear box/transmission is right above your head if you are sitting in the back. Since this part of the aircraft was designed to support the weight of the airframe while it is in the air it is significantly stronger than the cockpit. The rear wall (if the aircraft that you are in has such a thing) should be in the farthest aft portion of the cabin. Directly behind this wall should be the fuel cell, and believe it or not this is actually a rather rigid section of the aircraft.
-Helicopters do not like people.
This is no shit: aircraft don't like people. Do not anthropomorphize the machine, as it will in return immediately kill you for that complacency. If you start reading NTSB crash reports you will notice that one of the principle causes of a mishap is Pilot Error. Reading farther into the exact cause of the mishap you can usually find something along these lines: “instrument scan broke down,” or “fostered a cockpit culture of complacency.” Probably the most damning wording that I have personally seen in one of these reports would be this statement:
“Pilot lack of situational awareness and failure to grasp critical nature of emergency.”
-Where you are at will determine your fate.
Seriously, if you are inside the Height and Velocity Curves (see below) you are going to have a hard time of things depending on two main factors: airspeed and altitude. When a helicopter develops some form of an emergency, the pilot will immediately be forced to make a decision between one quantity and the other. Without some form of thrust from the rotor(s) you cannot have both at the same time.
Therefore if you are very low and very slow things are going to go poorly. A general rule is that if you are over 300 feet AGL (Above Ground Level) or above 30 KIAS (Knots Indicated Airspeed) and the pilot is competent, you stand a fairly good chance of coming out okay. The obvious caveat to that rule would be the quality of the landing areas immediately below your current position.
Both density (DA) and pressure altitude (PA) also play a role in how well the aircraft is going to perform. Despite the dual role of these figures in aviation, it is DA that will play a far greater role in the performance of an aircraft. The amount of air routed through the engines, over the wings (or rotors as is the case here,) stall speed and center of gravity are all going to be affected by density altitude.
The critical role in appreciating density altitude cannot be understated when it comes time to determining how the aircraft will continue, or if it will continue to function.
What You Need to Worry About
There are some specific things that you need to understand about helicopter emergencies, should you find yourself involved in one. What we are going to tackle here are Emergencies Inside the “Dead Man’s” Curves, Loss of Tail Rotor/Loss of Tail Rotor Authority, Static/Dynamic Rollover, Catastrophic Rotor System Failures and How to Survive Underwater Egress Situations.
Dead Men Don’t Write Manuals
Height and Velocity Curves are a set of finite limits also known as “Dead Man’s Curves.” Typically, if the aircraft is inside of this flight regime and a single/dual engine failure or similar catastrophe occurs it is unlikely that the aircraft is going to be induced to enter a mode where a successful landing can be made. In other words, you do not have the altitude or airspeed to land properly and you are going to crash promptly.
These particular aspects of aircraft performance are documented in the manual published by the aircraft manufacturer. This manual is called either the Aircraft Owner's Manual or the Pilot's Operating Handbook, and it should be somewhere inside the helicopter at all times. The pilot (again) should be able to produce this manual on demand. A sample Height and Velocity Curve chart looks something like the following:
Don’t be stupid. This is a sample diagram and not to be used as something approved by the manufacturer.
500 | |
300 |_ |
A |X\_ |
L |XXX\_ |
T |XXXXX\_ |
I |XXXXXXX\_ |
T |XXXXXXXXX\_ |
U |XXXXXXXXXXX\_ |
D 150 |XXXXXXXXXXXXX\ |
E |XXXXXXXXXXXXX| |
| |XXXXXXXXXXXXX| |
A |XXXXXXXXXXXXX| |
G 75 |XXXXXXXXXXXXX| == |
L |XXXXXXXXXXXX/ == |
| ============= |
| = _________________________|
0 30 60 90
KNOTS INDICATED AIRSPEED
Sample Height/Velocity Curve Chart
XXXX = Flight Regimes to be avoided.
==== = Preferable takeoff profile.
Take particular note of the annotation next to the Altitude axis marking, ‘AGL.’ In this case, AGL again denotes Above Ground Level, which means that it does not take into account Density altitude as discussed a little later.
Should you find yourself riding in a helicopter as a passenger, you need to pay particular attention to what the aircraft seems to be doing during the two phases of flight that this section concerns. Namely, these are take-off and landing.
-One helicopter at the mercy of gravity.
What to do in This Situation:
1. Pilot……………………PESTER (YOU)
If the engines have stopped or appear to be in the process of stopping, now is a very good time to pipe up and ask if there is a problem. If this is confirmed, press on quickly.
2. Seat/Harness……………………LOCKED, UP and TIGHT (YOU)
How to lock your seat belts should be explained to you, assuming that your aircraft is equipped with seats that have devices called ‘inertia reels’ installed.
These devices function just as the seat belts in your car do and lock when moved very quickly. Additionally, they should have some way of manually locking them so that you are essentially stuck to the seat.
Move the seat to the maximum upward limit possible (if adjustable) and tighten anything that you possibly can. The more you are a part of the airframe in this case, the better.
If there is available time after this step, attempt to jettison doors/windows (if possible) at this point. (Egress will become a much simpler process if there is no door for you to open after hitting the ground.)
3. Crash Position……………………ASSUME (YOU)
If you have a shoulder harness the crash position is as follows: Arms crossed over chest, hands in armpit with thumbs extended vertically and out of the armpit. Your feet should be flat on the floor with knees bent.
4. Impact……………………SURVIVE (YOU)
Okay, try not to mess this step up, Champ.
5. Aircraft……………………ABANDON (YOU)
It isn’t going anywhere and you sure as hell don’t need it anymore. Get away before it catches on fire and you find out how your ribs are going to be done.
What Constitutes Loss of Tail Rotor/Loss of Tail Rotor Authority?
This situation occurs when the torque or power required to rotate the tail rotor ceases to get through the aircraft’s transmission system to the tail and therefore to the tail rotor. This means that the force generated by the main rotor’s movement through the air is no longer being balanced out and the main fuselage of the aircraft will immediately begin to turn in the opposite direction.
-One helicopter spinning like the Tilt-a-Whirl at last year’s State Fair.
What to do in This Situation:
1. Engines……………………SECURE/FLIGHT IDLE (PILOT)
This may seem alarming, however the engines are what are supplying torque to the main gearbox and causing the problem that you are having right now. ‘Flight Idle’ is the condition where the engine or engines are running just enough to turn things such as the generator and hydraulic pumps.
2. Collective……………………DUMP (PILOT)
What we are trying to do here is decouple the head from the main transmission so that it windmills and slows down, thus slowing the rate at which the cabin is turning.
3. Left/Right Rudder Pedals……………………GET JIGGY (PILOT)
At this point you should be revolving right at a fairly rapid clip. You may have some limited control of the tail rotor remaining. It never hurts to try.
4. Seat/Harness……………………LOCKED, UP and TIGHT (YOU)
Spit out the gum. Go on. Spit that junk right on the floor too while you’re at it. Give the pilot something to complain about assuming that you get past Step 7.
5. Crash Position……………………ATTEMPT TO ASSUME (YOU)
Like before, if you have a shoulder harness the crash position is as follows: Arms crossed over chest, hands in armpit with thumbs extended vertically and out of the armpit. Your feet should be flat on the floor, your knees bent.
We say attempt to assume here because you are probably not holding on to your lunch at the moment, let alone neatly folding yourself into the textbook crash position.
Should you find yourself out of the seat during a Loss of Tail Rotor/Loss of Tail Rotor Authority situation, the best recommendation for surviving the now inevitable impact is to distribute your weight on the floor as evenly as possible.
Accomplish this by laying down spread eagle, with your body as flat on the floor as possible. DO NOT face directly down (nose pressed into floor) as you are likely to break your nose on impact. Press the side of your head (ear) flat down on the cabin decking.
6. Flare……………………EXECUTE (PILOT)
A ‘Flare’ is a maneuver that is executed just before landing. This will involve pulling up on the collective and pulling back on the cyclic that will in turn bring the nose of the aircraft up and hopefully very quickly slow your rate of descent. Unfortunately, you are going to start spinning very rapidly again as a result of the pilot pulling up on the collective.
7. Impact……………………SURVIVE (YOU)
If you do not survive the impact it is not necessary to proceed to the next step.
8. Aircraft……………………ABANDON (YOU)
It isn’t going anywhere and you sure as hell don’t need it anymore. Get away before it catches on fire and you find out how your ribs are going to be done. Don’t step on your gum, either.
The Airframe Has Fallen, and Can’t Get Up.
Dynamic rollover and static rollover are relatively unique phenomena related to rotary wing aviation. Dynamic rollover occurs when the center of gravity (referred to as CG from here on,) is moved laterally to the point where the rotor system actually pushes the aircraft over and onto one side. Alternately, static rollover occurs when aircraft CG is moved laterally such that gravity takes over and it simply falls over.
Dynamic rollover is usually a phenomena associated with shipboard operations of rotary wing aircraft and typically will not happen on land. The obvious exception to this would be a situation where the surface that the aircraft has landed on shifts or collapses beneath the landing gear and then causes the aircraft to fall.
Static rollover again is similar in that it is usually a condition unique to shipboard operations. Obviously, a ship in the open ocean tends to pitch and roll (violently on occasion,) and these conditions can lead to an improperly secured aircraft to tip over.
Obviously, most helicopters are not intended to fly inverted. (Although some certainly are capable of such maneuvers, those that are can only sustain this flight regime for an extremely limited period.) Therefore, when the aircraft rolls or tips over the effect is much like rolling a car either onto one side or onto the roof.
If you have ever seen an upside down automobile
you should have observed that the vehicle immediately began to dump various fluids critical to operation onto the ground. The same is true for a helicopter
laying on one side or another. Oil, hydraulic fluid, in some cases coolant, and fuel will all immediately begin to pour out of reservoir servicing ports (filler tubes) and various vents.
The biggest risk that you will face in a static rollover situation is the accumulation of these fluids around the airframe. Obviously, most of these fluids are toxic and an equal if not greater number are quite flammable. You will need to immediately evacuate the area and remain clear of the aircraft until the appropriate hazardous materials and emergency response personnel can arrive to properly secure the area.
Dynamic rollover on the other hand, will involve the violent destruction of the rotor head and at least some portions of the transmission system.
Composite materials such as fiber glass, carbon fiber and metals such as magnesium (from which some aircraft gearboxes are manufactured) are going to be your greatest concern. The fumes from burning carbon fiber and other composites are extremely toxic and should be avoided at all costs.
-One aircraft pushed one step too far.
What to do in this situation:
1. Aircraft Motion Ceased……………………CONFIRM (YOU)
This would include any bits of the aircraft that may be flying around due to the disintegration of the rotor system.
2. Engines/APU/APP……………………SECURE (PILOT)
APU/APP would be Auxiliary Power Unit or Auxiliary Power Plant. An APU or APP is essentially a very small jet engine that is used on larger helicopters to generate hydraulic and electrical power for critical systems when the engines are not turning. Smaller, more common civilian helicopters typically do not have an APU or APP and rely on ground or battery power alone prior to starting the engine.
2.A. Engine/APU Fire Extinguishers……………………DISCHARGE AS REQUIRED (PILOT)
Fuel and oil may be leaking out of case drains, pressure vents and servicing ports. Once this material hits a hot exhaust, the combustion or compression section of the motor it may indeed ignite. If this is the case, execute Step 3 as rapidly as possible.
Deluxe Bonus Knowledge Type Garbage You Can Derive a Smug Sense of Self-Satisfaction From Knowing:
All jet engines have five basic sections, these are (in order from front/suck to back/blow): Intake, Compression, Combustion, Turbine and Exhaust. An easy way to remember this is I-C-C-T-E, pronounced ‘ICK-TAY’. Vastly simplified this is Suck, Squeeze, Bang, Go and Blow.
Furthermore, jet engines come in the following flavors: Turbojet, Turbofan, Turboprop and Turboshaft. Helicopters almost exclusively use Turboshaft engines with the exception of those rare birds that still have reciprocating or piston-powered engines.
3. Aircraft……………………FLEE (EVERYBODY)
Poor airplane. All broken and needing maintenance. Sniffle.
We’ve thrown a rod.
Is that bad?
Catastrophic rotor system failures are neither funny, nor are they something to be treated lightly. This will be the shortest of all the emergencies as there is literally nothing that you are going to be able to do in order to stop what has happened.
This situation is not difficult to explain in terms of fixed wing aviation. You are in an airplane. The wings fall off. Now what?
-One helicopter shedding rotor system parts.
What to do in this situation:
1. Universe……………………MAKE PEACE WITH (YOU)
Good luck, fellas.
Water Egress Scenarios: Train Like You Fight, Fight Like You Train
This is the part where things become hard. When a helicopter impacts a body of water during an impact sequence, several things happen in very rapid succession. These include:
1. Anything that is not tied down in the cabin begins to migrate.
2. The aircraft rolls inverted and begins to sink.
3. Aforementioned migrating objects begin to float/sink.
4. You attempt to remove yourself from aircraft.
In the middle of this, ahem, pleasant situation here you are upside down, underwater, trying to escape, and sinking into the dark fast. If you are an average human being you have about three minutes of useful oxygen between the time that your head goes under and you pass out from hypoxia. When you take into consideration that at the time of impact you will be running at somewhere in the neighborhood of 150% of what you are used to, your oxygen supplies are probably going to last one and a half minutes. Maybe more, maybe less as physiology is not the same for everyone. The stress of being placed in a wholly abnormal situation such as this one may cause you to just up and pass out at the get-go.
-One helicopter entering the water.
What to do in this situation:
1. Windows……………………JETTISON IF ABLE (YOU)
If this is a planned ditch, then you are going to know before hand that you are going to make a water landing. If you smack the water with no warning, then other, far more significant issues are at work and you should probably skip straight to Step 3.
2. Crash Position……………………ASSUME (YOU)
Deviate from this as per below. Pitch anything that is not going to help you survive in the water at this point. As has been said before: Unless you want to wear it or eat it, get rid of the thing.
3. Point of Reference……………………LOCATE (YOU)
The general idea here is that the aircraft is going to roll upside down almost as soon as you enter the water. In locating this point of reference you are going to need to remember which direction that is relative to the surface of the water. In other words, pick something that if you go toward it, will lead you toward and not away from the surface. If possible, place your hand on something such as a window sill/edge to physically remind yourself. If you are sitting next to a window, the bottom of that window is an excellent place to use.
4. Flare……………………EXECUTE (PILOT)
See above for an explanation of what constitutes a ‘flare.’
5. Impact……………………SURVIVE (YOU)
Just a reminder.
6. Aircraft Motion Ceased……………………CONFIRM (YOU)
Allow the cabin to fill with water as well before attempting to exit your seat. The force of the water entering the cabin will promptly push you someplace ugly if you are unbelted at the time of impact.
7. Aircraft……………………EXIT (YOU)
Don’t worry about luggage either, you can claim it later as a travel expense. DO NOT INFLATE YOUR FLOTATION DEVICE AT THIS POINT. If you inflate now, you are going to be pinned inside the aircraft and unable to exit. This is bad as you are going to go for a ride and find out what the bottom of the body of water that you are in looks like. When you think you are clear of the airframe, give two strong kicks of your legs to make sure. If you don’t hit anything with your feet or legs, proceed to the next step.
8. Flotation Device……………………INFLATE (YOU)
Once you are on the surface, try to swim over and hang out with the rest of the survivors. Use whatever means you have handy as far as signaling goes, and wait for rescue.
Used for general reference and information concerning rotary wing aviation.
Source of the sample Height and Velocity Curve diagram above, as well as an explanation of same.
Mishap statistics and reports for aviation.
United States Navy mishap survival and information.
-United States Navy Aviation Water Survival School
Water survival with specific regard to the concerns inherent to rotary wing aviation. Note: I have not attended class, however I have spoken with numerous individuals who have and the material provided is culled from those conversations.