Would a roll cage plus a safety harness make a small GA aircraft accident more survivable?

Question

It seems to me that race cars (like Formula 1 and NASCAR) and small GA aircraft (like a Cessna 172 or Piper Cherokee) travel at generally the same speeds, roughly between 70 and 200 mph. Yet, if an accident happens, you appear to be more likely to die in a small plane than a race car.**

I figure this may have to do with some of the safety features of race cars versus the safety features of GA aircraft. The main features being the racing harness and the roll cage. (And also, as Freeman pointed out in a comment, the HANS device and the helmet help quite a lot as well, especially in frontal impacts.)

I know roll cages weight about 80lbs and that they aren't cheap, and I know a safety harness can be difficult to put on and people might not like using them, and I know a HANS device can be cumbersome, as also a helmet can be. But forget all of that for a moment. I'm not asking about why we don't use them from an economic/utility perspective.

What I really want to know is if putting these in a small airplane would be of any benefit to begin with. It's true that they are massively helpful in racing vehicles, but I wonder if the forces racing vehicles face during a crash are markedly different than what you would find in your typical GA crash (e.g., perhaps aircraft accidents happen at less predictable angles, or involve more torsion, etc.). And if perhaps those differences in forces make the use of a roll cage and a safety harness kind of pointless in a small plane because they can't actually help in that kind of accident.

So, would all of these racing safety devices actually make a GA crash more survivable, or does the nature of GA accidents make their use less effective than they are in a race car?

** Try as I might, I couldn't find hard stats on "deaths per accident" in either area. So this is mostly an impression I've gained from reading a lot of NTSB reports and watching a lot of racing. The fact may be debatable, but shouldn't detract from the main question.

Answer 1

Short answer: Yes, a better harness would help in some cases, but will achieve little all by itself. A roll cage might help in a few cases, too, but would be much less effective per pound.

Your observation is correct: Race car drivers enjoy a lot more protection than GA pilots. This is a rather recent development; 30 years ago the chances of surviving a crash were equally low for both. However, while car crashes involve mostly horizontal accelerations, airplane crashes might show accelerations from all sides. Simply put: Car drivers need protection mostly in one direction while the same protection will help GA pilots and occupants only in some cases.

There are two factors which stand out in a GA crash:

1. Peak accelerations which will lead to internal lesions like the rupture of the coronary blood vessels, and
2. Physical injury by sharp objects entering the occupant's space, including flailing limbs being hurt by sharp objects in the cabin.

Both factors were also killers for race car drivers, and they were defused with improved design methods. A safety cage is not just a frame around the driver: Any structural failure must occur in such a way that the structure fails away from the driver. In addition, the whole car body is designed to crumple at roughly the same force over its length in order to use the available crumpling zone as well as possible. This allows to decelerate the safety cage at a constant rate, so that peak loads can be avoided. A third factor is a much better restraint system, of which the HANS device is only one aspect. Using five-point harnesses would already help to avoid "submarining", a process where the pelvis slides under the lower restraint, causing the harness to press against the intestines. The image below shows the regular pelvis location and body contours as a dashed outline and the displaced pelvis and spine as a solid line. The displaced body is the shaded area.

None of this was considered at the time when today's GA aircraft were developed and the regulations were set up. At that time the prevailing opinion was that nothing could be done in a crash, so all efforts focussed on avoiding crashes in the first place. Adding only parts of the whole protection packet will be of little help - only their combination can effectively protect the race car driver. Even the 5-point harness needs an adequate seat and properly located mounting points to be effective.

The US army has collected all research up to the early Eighties in a five volume work called the Army Aircraft Crash Survival Guide (pdf!). It's intention is to improve the crash survivability for helicopter occupants and Army aviators, and much can be transferred to General Aviation. If you look for hard stats, you will find at least lots of citations there. I remember in particular a study from the Fifties where statistics showed that J-3 pilots would mostly be killed in a crash, while the rear occupant would show only minor injuries. In the study, Pipers filled with test dummies were put on rails and crashed into an earth wall. Funny stuff.

A J-3 in Army livery. Then it was called O-59 or L-4.

Answer 2

Disclaimer: I am the VP at HANS Performance Products, makers of the HANS device. I know a little about cockpit safety but am new to the field of GA safety.

Drivers survive horrific crashes in auto racing because they are extremely well contained. A 360-degree surround seat (often called a full containment or halo seat), a multi-point harness, fireproof suit, gloves and shoes plus a helmet and head restraint are used to contain the driver. This often results in drivers surviving 100g impacts (not the 10g mentioned above). For example Ritchie Hearn hit the concrete wall at Indy at 129g and suffered only a broken foot. He was wearing a HANS device.

Although many race cars can exceed 250mph it is the rate of deceleration that causes injury. In this I think GA and auto racing accidents are similar. In fact EMT crews often talk about high speed racing accidents as airplane accidents on the ground.

There is no single magic bullet to cockpit safety. Here is a short video on the topic that may be useful to GA pilots and engineers.

Answer 3

The short answer is no. But if you are curious as to what it would look like check this out.

Racing accidents are generally different than GA accidents. Although race cars often slam straight into things they tend to have what is called an Impact attenuater out front. Since F1 cars are mid engine the nose is often left empty and can house impact absorbent materials. Planes are limited in this by having a propeller out front (unless its a small twin).

Roll cages in cars help to protect against (lets not be silly here) but rolling, something that F1 cars can do if they say, corner to hard and fly off the track. The thing to remember here as well is that a car only really moves in the X-Y plane. It is easier to predict how a car will and can hit something by limiting the range of motion. A plane can hit the ground at almost any attitude in any configuration in the X-Y-Z plane. This means the cage would have to be much more through. Keep in mind as well that a roll cage in a car just protects the driver, not the whole car. While you could have a roll cage just around the area that people are sitting you still have a weight issue.

Lets ignore the weight for a minute and think about when a roll cage could help a plane. If you were coming in for an engine out approach and something happened at a low altitude causing the plane to hit the ground and roll you may see some benefit. If you botch (and lets hope you never do) a landing you may see some benefit if the plane rolls over or hits something.

When it wont help, any kind of nose dive situation or sever ground impact its not going to get you much but it will get you something. In this case you want something that will absorb the shock not stay intact and transfer it to you.

It has been brought up that auto racers also wear things like wrist restraints, neck braces, helmets and harnesses. Having worn these things before I can confidently say that it is very difficult to move around in them but when driving a race car you only really need to see straight in front of you and a bit off to each side. Flying VFR would be tough if you were that strapped in and had to move your head around to look out the window.

While we are on the topic (although a bit unrelated) a fire retardant suit like the ones worn by F1 drivers could provide some protection in certain aviation style accidents as they do provide a very real, very measurable amount of protection. The best example I can think of is a serious cabin fire that somehow exists in such a way you still have control over the plane. In this case the suit may buy you enough time to get the plane on the ground and egress safely.

The real issue also comes down to cost. Are you willing to sacrifice 80-150LBS of useful load to tote around a cage that is not really going to make anything that much safer. Carbon composite shows a lot of promise in this field by simply making stronger and lighter frames but for what its worth these things are still not cheap. And lets be honest there are lots of things, like full air frame chutes, individual parachutes etc, that would make flying safer, but at some point you have to assume some risk to successfully partake in the activity.

EDIT

After some research I found out that Mooney implements a roll cage of sorts into its design see this article for some notes on it. This video claims that the newer Mooney has a "NASCAR designed roll cage to keep the occupants safe. This Thread brings up some interesting points on roll cages and reenforced structures vs the Cirrus full fame chute and may be worth a read. Although Mooney does have a roll cage of sorts my previous points still hold true in respect to ADDING a roll cage. The Mooney cage is part of the airframe its self and is there from day one of design.

Answer 4

A HANS device seems like it would be a non-starter because pilots need to be able to move their head during normal flight. Unlike race car drivers, pilots are concerned with more than just what is directly in front of them or to their left. Also, they need to be able to grab stuff out of the back, adjust radios on the other side of the cockpit, etc.

In most cases, a GA aircraft 'crash' will be less violent (i.e. lower instantaneous acceleration) than a car slamming into another car or a wall. While this isn't always the case, in most cases a crash is either just sliding off the side of a runway or landing on something that isn't meant to be landed on, not usually impacting something head-on. Additionally, aircraft generally don't roll. They might flip forwards over the nose, but rolling is rather difficult, given the length of the wings. The wings would usually have to break off or the roll would have to happen while airborne and then crash inverted in order for the aircraft to 'roll.' As such, the added weight of the roll cage would generally not be worthwhile, especially since it would be a very significant portion of the overall weight in a light aircraft, which matters a lot more than the weight of a car.

As far as more complicated restraints, they would have to be very quickly and very reliably removable. Fires are a big issue in light GA crashes, so the ability to get out ASAP is very important.

As far as helmets are concerned, while these might make sense in aircraft that are operating in conditions where a crash is more likely (racing, aerobatics, etc.,) it seems like their annoyance in normal use would outweigh the benefit in the still rather unlikely scenario of a crash. Even from a pure safety standpoint, annoying/restricting/distracting the pilot seems likely to cause more fatal accidents than it would prevent. In general, I'd say the reasons are pretty similar to why we don't wear helmets when driving down the highway, even though my car will be moving faster on the drive home from the airport than my plane will be moving on touchdown. The cost/benefit ratio is just too high for it to be worthwhile.