Thursday, December 10, 2015

At Last, Real Cat "A" Performance From A Twin Engine Helicopter at Gross Weight...

Jeff and I are riding over to his house near Penn State University for a visit. The years apart have vanished and we have taken up right where we left off, both eager to talk helicopters and HEMS. He tells me about his trip to AMTC in St. Louis  a few years back, paid for by Eurocopter (now AIRBUS Helicopters) so that he could stand next to Geisinger's new ship on display. He assures me he sold several aircraft on that trip, and was offered a sales job. That boy can talk - when the two of us both get going at once, cabin O2 levels drop.

Our conversation moves onto the newest variant of the BK, the AIRBUS H145T2. We discuss how it got certified. As you may know, the type certificate claims that an EC145 is really a BK-117C2. The company saved themselves a ton of money by saying that the 145 was simply a modified BK. Yes, sure, if you consider different engines, different fuselages, different engine monitoring systems, and different cockpit layouts simply "modifications" to an original. Now, with the addition of a fenestron the only thing about a H145 that resembles a BK is the rigid "blades bolted to the mast" rotor system. The French half of the marriage that made Eurocopter/AIRBUS got their way and added a fenestron, too bad they didn't add a starflex rotor system as well. The BK rotor system sucks, when in the clouds in turbulence.

Jeff says, "it's the first one with true Cat A capability." I hadn't thought much about Cat A lately, because here in America operators aren't required to comply with Category A takeoff requirements. We could, but we don't. It would reduce our payload and fuel range too much.

What is CAT "A"? Basically, it's a set of standards and procedures that result in a twin engine helicopter never being in a position from which a single engine failure will result in a crash. Most twin engine aircraft will not hover at maximum gross weight with one motor off-line, but Jeff assures me that the new 145 will. That is going to change how departures are made in this machine, I suspect.

Dare County Med Flight is the US launch customer for the H145T2
The addition of a fenestron makes the ship easy to identify.
If you want to read more about Category A standards, click here...

A category A takeoff looks different than a "normal" takeoff. As the pilot brings the aircraft up to a high hover, she backs up slightly, keeping the pad just departed from in view down below and slightly in front. Once at a "takeoff decision point" the ship is rotated and flown away. If a motor quits prior to rotation, we are going back to the pad. If a motor quits after rotation (pitching the nose down to accelerate) we will fly away on one motor. Likewise, on approaches the aircraft has enough power to land on one motor, without bending metal. When I got checked out in an EC-135, we practiced engine failures (using the FADEC's training mode) on approaches, and the 135 has near flyaway capability, but I am not sure it would meet true CAT A capability at max gross weight. The Bell 222s and 230s I flew years ago would have laughed at me if I mentioned CAT A. In those ships, the second engine would do no more than fly us to the scene of the crash. As happened here..

Luckily, motors don't quit very often. And we fly singles here every day. This is perhaps why, here in America,  Cat A capability isn't required. The airlines have a different deal. A twin engine airplane must have enough runway to accelerate to flying speed at which point the pilot makes a decision to abort or continue. There must be enough runway to stop safely from that decision point. They call this number of feet of runway required the "accelerate-stop distance." The aircraft must have enough power to fly away on one engine from that decision point. These requirements guarantee  the safety benefit of having two motors.

Here's hoping no one ever has to use the Cat A capabilities of the new H145T2. But it will be comforting to know that the capability is there, just in case.

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