Although new technology is being added to the cockpit at an exponential rate, it can be argued that performance is what ultimately still sells aircraft. And in that business of selling aircraft, helicopter manufacturers are always trying to maximize the performance they can offer in their various models as they try to fill each market niche. An operator can be thought of as being in its own business: the business of managing risk. To that end, we are always in search of the perfect aircraft that will accomplish our mission at minimum cost, but with maximum safety.
Despite the dizzying array of different models, as part of certification, every helicopter falls into either Category A (CAT A) or Category B (CAT B). CAT B aircraft do not have to provide any guaranteed “stay-up” ability after an engine failure, so by default, all single-engine helicopters cannot be certificated CAT A. But for that matter, not every twin is certificated CAT A because they don’t meet other design criteria or because they perform too poorly staying aloft on one engine.
In simple terms, helicopters certificated under Category A standards can guarantee that in the event of an engine failure, the flight can continue safely. CAT A provides the most rigid rules, requiring independent engines, fuel systems and electrical systems. It also requires that no single failure in these areas can cause simultaneous loss of two or more engines.
The ability to guarantee continued flight is without a doubt very appealing to every pilot, passenger and owner/operator. It can be a very competitive selling point to helicopter manufacturers who proudly advertise their helicopters' CAT A performance abilities. Yet as much as a no-brainer it would seem to be, there is a lot worth looking into when deciding whether or not to pay the premium associated with CAT A.
The wish to completely eliminate the height-velocity diagram by designing a helicopter with powerful enough engines is a grand one. How fantastic would it be to have enough power to lose an engine (OEI) during any portion of your flight, at any operational weight, and have it be a virtual non-event? The trouble with this ends up being the “cost” of physics. The specific fuel consumption of engines with that much excess power and the heavy transmissions required to handle them conspire against us, necessitating the need to limit OEI performance for an affordable compromise (i.e. derated engines and lighter transmissions).
As a result, you’ll be hard-pressed to find many helicopters that have complete single-engine fly-away capability right from the helipad at all allowable weights and conditions. So to guarantee the stay-up ability dictated in the CAT A standard, manufacturers provide a specific set of flight profiles, along with performance charts that must be followed in order to guarantee safe passage along the entire flight path from beginning to end in the event of an engine failure, thus eliminating the H-V diagram. That’s the good news. The bad news is that for the guarantee, operators will have to accept performance hits in range and payload. This can also translate to less options if on an IFR flight plan.
So what’s the alternative? Well, it’s what the rest of us non-CAT A operations must accept: exposure. “Exposure” is what we have when we are in that portion of flight, usually takeoff or landing, when an engine failure can result in a less-than-safe landing; probably with a good engine still running, if we are in a twin. We are exposed to the unbendable laws of physics.
If you fly to and from a hostile environment such as an oil rig, and either your operation or governing agency regulation requires you to fly to the CAT A standard, then your ability to stay out of trouble is dependent on both your proper flying technique for your particular environment and adherence to the performance charts in the flight manual. Anything less will not guarantee your outcome.
Of course we all know that there are no guarantees in this business and certainly plenty of other ways always to crash a helicopter. With the reliability of today’s engines, perhaps an operation’s money would be better spent not on a CAT A capable model, but on one that has all the latest ground proximity warning/collision avoidance equipment. Or maybe it is better spent on training to avoid inadvertent IMC or controlled flight into terrain. Every operator must decide this for itself. This debate will and should continue, as the business of risk management is good for all businesses, and the only thing that’s truly ever been guaranteed in this business is the physics of gravity.
Frank Lombardi is an ATP with both fixed-wing and rotary-wing ratings. He began his flying career in 1991 after graduating with a bachelor’s degree in aerospace engineering. He has worked on various airplane and helicopter programs as a flight test engineer for Grumman Aerospace Corp. Frank became a police officer for a major East Coast police dept. in 1995 and has been flying helicopters in the dept.’s aviation unit since 2000. He remains active in test and evaluation and holds a master’s degree in aviation systems flight testing from the University of Tennessee Space Institute.