Parachutes, ejector seats and whole airframe recovery systems
- Credit: Keith Wilson
Parachutes and aeroplanes share a rich history, from the first sketches by Leonardo da Vinci to the most modern systems designed to save both the aircraft and its occupants. Dave Unwin takes a look at the aircraft recovery systems used today in GA
To BRS or not to BRS, that is the question. Or, at least, that might’ve been the question if the Bard both flew microlights and was willing to pinch a company name (Ballistic Recovery Systems, Inc.). Now, you might think that, as soon as aeroplanes could fly to heights from which you would not want to fall, the parachute was a logical invention. But in reality it pre-dates the flying machine by a considerable margin, as the earliest record of a parachute-like device can be traced as far back as 852AD−although its generally accepted that Leonardo da Vinci set out the first viable design around 1485.
Leonardo sketched a wooden frame, which changed the canopy’s shape from conical, as it was envisioned previously, to pyramidal. It seems unlikely it progressed past a sketch, but such a design was subsequently proven to work in the 20th Century. Venetian polymath Fausto Veranzio then dispensed with the wooden frame around the year 1615, while the first modern parachute was invented−and demonstrated publicly−by Frenchman Louis-Sébastien Lenormand in 1783. Lenormand also invented the word ‘parachute’ by neatly combining the Italian prefix ‘para’ (to resist or guard) with ‘chute’ (French for fall).
Early aircraft parachutes
Early parachutes used a canopy made from linen, but by the early 1800s they were made from silk, and featured a vent to reduce a tendency to oscillate. A century later and the parachute had evolved into being carefully folded into a back pack, which was deployed by a static line. By 1911 a jump had been successfully made from a Wright Model B, and by the end of WWI German fighter pilots were wearing them in combat. The Royal Flying Corps (RFC) never issued them to pilots as they reasoned it would reduce a pilot’s will to fight, although for balloon observers on both sides they were standard issue.
After the war Major Hoffman of the United States Army led a team tasked with developing a viable safety parachute. The team, which included Leslie Irvin (who went on to found the Irving Air Chute Company) pulled together all the best aspects of various parachute designs, ending up with the parachute being carried in a soft backpack, deployed by a ripcord and extracted by a small drogue ’chute. This is essentially the design still used today, and its inherent ‘rightness’ is clearly illustrated by the fact that within twenty years the Irving Air Chute Company was the biggest parachute manufacturer in the world (the illegitimate ‘g’ in ‘Irving’ was inadvertently added by a secretary when the company was formed, and not dropped until the 1970s).
Tens of thousands of aircrew saved their lives with an Irving parachute, but towards the end of WWII aircraft speeds had simply become too high and the air loads (dynamic pressure or Q) too great to enable a manual bail out, while the greater masses, substantial wing loadings and high stall speeds of jet fighters reduced the probability of a successful forced landing. So, it was time to invent an ejection seat but, contrary to what you might think, this invention was not British. German company Junkers had pioneered the concept with a late-1930s patent for a ‘bungee-assisted escape device’. Fortunately for German airmen of the period, the idea never progressed past the patent application paperwork. However, as both Dornier’s Do-335 and SAAB’s J21 had pusher propellers,the requirement for some sort of ‘assisted bail-out’ system was self-evident, particularly to pilots!
Ejector seats have saved more than 7,000
The German He 219 night fighter had seats propelled by compressed air in service during WWII, while in Sweden SAAB soon realised the limitations of compressed air and designed a seat that used explosives. However, it was engineer and inventor James Martin who fully appreciated that the introduction of jet aircraft and their commensurately higher speeds made the development of a reliable escape system imperative, and the rest−as they say−is history. A very brave Martin-Baker employee called Bernard Lynch made the first in-flight test, when he ejected from the rear cockpit of a specially modified Gloster Meteor at 8,000 feet and 300 knots. Incredibly, Martin-Baker still uses modified Meteors today for seat testing, mostly because the widely-spaced centrifugal-flow engines make them perfect for this mission.
The first emergency use of an M-B seat was on 30 May 1949, when Armstrong-Whitworth test pilot Jo Lancaster ejected from the prototype A.W.52, and since then the company has delivered more than 75,000 seats. In fact, the Mk7 seat alone has saved more than 2,400 pilots, while the overall total is currently 7,645−two pilots ejected from their Hawk on 25 March this year. Crew have ejected at supersonic speeds, well above 50,000ft, and even underwater. Hundreds of pilots have ejected twice, and a very select few
While evaluating various fast jets over the last twenty years I’ve sat on a variety of M-B seats and I’ve also flown sitting on other manufacturer’s seats, including the SAAB unit fitted to the Folland Gnat, and the AeroVodochody L-39’s VS1-BRI. Regardless of the manufacturer, it is irrefutable that ejection seat technology has come a long way. Indeed, I remember that strapping into the DH Vampire T.11 was quite complicated, as you had to fasten the parachute harness, leg restraints and seat straps separately, while the proximity of the two seats was also an issue: one of the pre-start checks was to pass a hand between the seats to confirm you’d not accidentally used each other’s straps!
Although the Mk3 fitted to early jets was fully automatic and had a minimum operating envelope of 200ft and 90kt it was, quite literally, a ‘bang seat’. Pulling the handle fired what was essentially a 40mm artillery shell and two smaller secondary cartridges, and these shot the pilot out with quite brutal acceleration to 80ft/sec. Subtle it wasn’t, and although the Mk3 saved over 250 lives, injuries−particularly to the back−were common.
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Some pilots, perhaps understandably, were also nervous about flying around while sitting on that artillery shell. When the Meteor F.8 (the first version to be fitted with ejection seats) began to arrive at frontline squadrons, some veteran pilots (many of whom had already bailed out of a Spitfire or Hurricane) specifically forbade the ground crews to pull the safety pins! Modern seats have a zero/zero capacity (you can eject while stationary) and use a combination cartridge/multi-tube rocket system which is much kinder to the back. Strapping in is also a lot simpler.
Other escape methods included encapsulating individual crewmen (as on the North American Valkyrie) and the F-111’s cockpit, which also functioned as an ‘escape capsule’. The piston-engined Skyraider’s ‘Yankee’ system used rockets to yank the hapless occupant clear of the cockpit. There’s a video of it being tested on YouTube, and it appears to have little to commend it!
Civilian ejector seats
For a long time military aircrews were reasonably well catered for (the scandal of only the pilots of the Valiant, Victor and Vulcan having ejection seats notwithstanding) and sporting aviators, such as sailplane and aerobatic pilots, could buy sophisticated fast-opening emergency chutes.
For those kind of civilian applications, a Russian company called NPP Zvezda even patented a lightweight pneumatic ejection seat system for the ‘normal’ operations of general aviation aircraft. The firm now builds two ejection systems: the KS-2012, which is designed for airspeeds up to 135kt and altitudes from 100ft to 13,000ft, and the KS-2010, which has the same altitude operating envelope at speeds up to 215kt. Compressed air is used for both, pressurised to an impressive 220 Bar (3,190psi) and there’s a metal telescopic ram integrated with the seat.
When the pilot pulls the handle, the pneumatic system releases the canopy latches, the airflow takes the canopy and then the ram pushes the seat upward until it and its occupant are clear of the tailplane. A drogue chute then automatically deploys to pull the parachute out. NPP Zvezda says the whole sequence takes ‘less than a second’.
I inspected one of the seats at AERO several years ago and it seemed perfectly plausible for something like an Extra or Sukhoi. While that may work in a powered aeroplane, when it comes to modern sailplanes there’s a problem, since the narrow cockpit and reclined seats make abandoning the aircraft difficult.
In 1995, German sailplane manufacturer DG Flugzeugbau patented the NOAH (NOtAusstiegsHilfe – literally ‘emergency exit help’) system. This system uses a device like a car’s airbag, which is installed under the pilot’s seat. When the pilot decides it is time to leave, they simply pull a handle which inflates the airbag and pushes the pilot up and out.
One very clever, simple design that I saw when I tested an early Me-7 World Class sailplane was a section of the cockpit floor about the size of your heel was recessed to assist you when baling out.
Why not try to save the whole aircraft?
So, several options exist for sporting aviators, but what about other GA pilots and−more pertinently−their passengers? An initiative that had its origins in the hang glider movement began to gain traction in the 1990s: the idea of recovering the whole airframe.
Although the well-known Cirrus series were the first certified aircraft to be fitted with a recovery system, the Cirrus Airframe Parachute System (CAPS), developed jointly with Ballistic Recovery Systems Inc, is actually not a new idea. Some hang gliders were fitted with relatively crude, hand-deployed emergency parachutes as far back as the late 1970s, while the first ballistic systems, which were based around a projectile thrown out by a charge similar to a 12-bore shotgun cartridge, began to appear in the early 1980s. However, to deploy a parachute large enough to recover an aircraft weighing over 2,700kg, rocket propulsion was clearly the way to go: most modern units in fact use small, high-energy rockets to pull the parachute canopy from its container.
Ballistic Recovery Systems Inc of Minnesota has now been selling these systems for nearly two decades, and has delivered nearly 14,000 units (mostly to non-certified sport aircraft). BRS also continues to supply the CAPS units to Cirrus Aircraft in nearby Duluth, and all Cirrus aircraft, from the original entry-level SR20 of 2000 to a 2021 model Visionjet are delivered with CAPS as an integral part of the airframe.
Most pilots would probably attempt to force land after an engine failure, but should the situation clearly be irretrievable (say after a mid-air collision, structural failure or an engine failure over impossible terrain) then the Cirrus pilot has one more card to play by pulling the red CAPS handle. This used to fire a magnesium charge which ignited a powerful solid-fuel rocket, but these days the igniter is electrical. Approximately 20kg of pull force is required. The rocket shoots through a frangible hatch aft of the baggage bay and pulls out a parachute canopy 16.8m in diameter.
Cleverly, the problem of the canopy shredding itself when deployed at high speeds (it is certified for use up to 134kt, although I believe it has been successfully deployed in excess of this) was solved using an innovation initially developed for ram-air type skydiving parachutes. During deployment, a ring near the canopy slides down the rigging lines to the parachute’s risers, restricting the rate at which the lines can spread and reducing the speed at which the canopy inflates at high speed. The ‘slider’ does not impede the rate at which the canopy inflates if it is deployed at low speed. Very clever.
Once fully inflated, the parachute lowers the aircraft to the ground, and although at touchdown the sink rate is around 1,700fpm and far from gentle, it is survivable. The CAPS weighs approximately 25kg, and to date over two hundred lives have been saved, the most recent use occurring in April after a mid-air collision near Denver. This was the 123rd time CAPS had been activated, and both occupants survived uninjured. Of those 123 activations, 104 resulted in the parachute successfully deploying, and there were 212 survivors and one fatality. Not s single fatality has occurred when the parachute was deployed within the certified speed and altitude parameters.
Whole-airframe recovery is popular with microlights
Many high-end modern microlights and Light Sport Aircraft (LSA), such as the Flight Design CT series and Pipistrel Alpha, are also fitted with some form of whole-airframe parachute recovery system, as either an option or standard equipment. However, unlike CAPS (which has the risers built into the composite airframe during manufacture), these systems are more like add-ons.
The main players are the aforementioned Ballistic Recovery Systems Inc, Galaxy Rescue Systems, Magnum USH, and Junkers Profly. All of these systems use pyrotechnic devices (essentially solid-fuel rockets) to extract the canopy, and either mechanical or electrical igniters.
The mechanical devices consist of a plunger driven by a steel spring, dual firing trains and a firing pin actuator attached to the operating cable. Each firing train consists of a pin and primer (or percussion cap) which ignites a mixture of black powder (used because of its thermal stability) and magnesium called the primary booster, at the end of the igniter.
On larger systems, the primary booster ignites a secondary black powder and magnesium booster in the rocket motor’s base to ensure ignition. In its normal position the firing pin actuator and plunger are interlocked with two small ball bearings held in place by the inner wall of the igniter body. Since the spring is uncompressed and the plunger is separated from the firing pins by a 0.060 inch gap, the igniter cannot fire. Pulling the handle initially ‘takes up the slack’ (which is there to prevent inadvertent actuation) and then compresses the spring and ‘cocks’ the plunger, just like the hammer on a single-action revolver. Keep pulling (as you’d certainly be well-motivated to!) and the ball-bearings are released, separating the handle from the plunger, which strikes the firing pins with the energy of the compressed spring.
Pyrotechnics or Compressed air?
The primers, black powder, magnesium and solid-fuel rocket, however, combine to make a powerful pyrotechnic, and that is a problem. Whenever any government agency or freight handling company sees the word ‘pyrotechnic’ they get nervous. Consequently, recovery systems can be become an issue, as they are not straightforward to ship−especially since the UK left the EU. Import duty has also increased, and none of these sytems are manufactured in the UK.
Another factor to bear in mind is that the typical service interval for a recovery system is usually around six years, so if the one you’re planning on fitting to your microlight is attached to a solid fuel pyrotechnic device expect to pay around £4,000 to purchase the unit, and another £1,500 (plus shipping) every six years. These are sizeable sums for an aircraft that may only be worth £20,000 to begin with.
One way around the pyro problem is−as demonstrated by both Heinkel and NPP Zvezda−to use compressed air. Using compressed air instead of a rocket is an interesting proposition that confers at least one significant advantage: the device can be shipped unpressurised. Compressed air systems should also be easier to service, possibly even by owner/operators.
The concept clearly has merit, and an American company called Second Chantz developed and marketed a compressed air system during the 1980s which did find favour with microlight pilots. Eventually the company was bought by BRS Inc, but the latter eventually shelved the compressed air technology in favour of their own pyrotechnic-based system.
An Italian company called Comelli still makes compressed air systems, which are very much aimed at aircraft on the lighter side of the sport flying spectrum, such as hang gliders, paragliders and paramotors. The most powerful system they produce is only rated up to 472.5kg.
Another decision that an operator has to make, besides choosing between a pyrotechnic or a pneumatic system, is whether to have the canopy carried in a fabric container called a ‘softpack’, or an aluminium canister. Softpacks are generally lighter and cheaper, but not smaller, than metal canisters, and are often popular with the owners of SSDR (Single Seat Deregulated) aircraft because of their reduced weight. They are also easier to inspect but are more susceptible to weather contamination, such as rain, snow or fog. Some manufacturers, such as Magnum, even offer a system which utilises multiple softpacks for aircraft weighing up to 1,796kg. The alternative system uses an aluminium canister for the canopy.
The advantages of a canister over a softpack are that the sealed canister protects the canopy from the elements and that it allows the parachute to be pressure-packed, making the entire system significantly smaller. As most BRS parachutes have deployed diameters considerably wider than the wingspan of the aircraft they’re fitted to, pressure-packing it into a canister system reduces the system’s size while only adding a little extra mass. In any case, irrespective of whether a canister or a softpack is used, the parachute is essentially the same in the two systems. However (and unlike CAPS, which was rigorously tested) the systems built for microlight and permit types have not been tested in all kinds of scenarios. These retrofittable parachute recovery units can be fitted to dozens of different types, and it simply is not possible to test inflight deployment over a range of attitudes, speeds and situations for so many different aircraft. They are fitted on the basis that they might work−interestingly, in the UK the CAA approves their carriage, but not their use.
So, should you fit one? The probability of ever needing it is quite low−although conversely if you do need it, then you’ll really need it! They are expensive (both to purchase and service, particularly pyrotechnics) and do reduce your payload, and of course there is the small matter of flying around with what Flylight’s Paul Dewhurst describes as an “exploding suitcase” on board. He also told me a very sobering story about a friend of his who crashed his Bristell in France and nearly bled out in the wreck. The rescue crew had spotted the red warning triangle and large yellow-and-black edged frangible panel, correctly concluded that there was an armed and powerful pyrotechnic in the fuselage and hung back for over twenty minutes before approaching.
Personally, I subscribe to the point of view of the great Ernest K Gann, who once wrote ‘if an airplane is still in one piece, don’t cheat on it. Ride the bastard down’. However, there are situations where I’d consider using a recovery system: in the USA LSAs are routinely flown at night, and a forced landing in the dark would certainly meet my definition of ‘character building’. Even in the UK you can fly over some very inhospitable terrain where a successful forced landing would be extremely difficult, if not impossible. On those occasions knowing that an aircraft parachute will give you ‘one more roll of the dice’ might boost your morale slightly, when the engine goes into ‘auto-rough’!
When to "pull the handle"
BRSs initially became popular with the Cirrus SR20 and SR22 models. At the beginning, however, those aircraft recorded quite a high fatal accident rate, which may seem counter-intuitive. It seemed that pilots were unsure as to when to ‘pull the handle’ and delayed its use until it was outside the speed/height operating envelope, or that when they were extremely stressed they would forget it was there - after all, it was a new device.
As with the Meteor pilots mentioned in the article, there may also have been a reluctance by experienced pilots to use it. Cirrus addressed these issues by changing its training of pilots, and its types now have some of the lowest fatal accident rates of any SEP.
In many ways, a Ballistic Recovery Parachute System should be viewed in much the same way as an ejection seat. It is an emergency device designed to save life, and its use will almost certainly result in the loss of the airframe and quite possibly injury to the aircraft’s occupants.
The advice offered by the manufacturers of various BRS-equipped aircraft is all essentially the same: you should pull the handle only when a forced landing cannot be carried out. Typical scenarios would be, for instance, a structural failure, losing control of the aircraft, an engine failure over inhospitable terrain, and pilot incapacitation.
A key aspect of using a BRS is to use it within its intended parameters, and this is highlighted in all the manuals I have examined. The SR22’s POH, for example, emphasises the importance of understanding that the fatalities that have occurred in Cirrus aircraft accidents may have been avoided if pilots had made the timely decision to ‘pull the handle’. While researching this piece I also watched a very interesting USAF video called “Ejection Decision – a second too late!” that made the same point: it emphasised that whenever an ejection resulted in a fatality, it was almost always because ejection had been initiated outside the seat’s envelope.
The aircraft manuals I read also highlight that the use of a BRS does involve risks, and should be evaluated against other courses of action. The Pipistrel Alpha’s POH for instance explicitly says that ‘the phase following parachute deployment may be a great unknown and a great adventure for the crew’, while the SR22’s POH states that ‘its use should not be taken lightly’.