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Friday, January 15, 2016

Why Does My Pilot Fly Differently Than Your Pilot?

True CAT A only applies to multi-engine helicopters.


Recently, a friend shared a bit for our blog, and observed that two different aircraft departed a rooftop helipad with different techniques. This led to complaints from an anonymous person in the comments area of the blog. This person was upset that HelicopterEMS.com had allowed the writer ( a non-pilot!) to share concerns about HEMS flying, and how HEMS pilots fly.While it won't be the norm to respond to someone who won't sign their work, this topic is worth more consideration and explanation.

With two fatal helicopter crashes in less than a week and five total last year, (three of those from within the same company) we think it is only normal for the crews who get flown in HEMS aircraft to take an interest in the nuts and bolts of pilot technique. To date, no nurse or paramedic has killed a pilot in a HEMS crash. It has always been one of us pilots flying everyone to the crash site. If they didn't take an interest in why and how we do the things we do, they might be considered dumb and clinicians aren't dumb. One of the purposes of this blog and the facebook page that goes with it is to reduce fear, suspicion, anger, and resentment that - unfortunately - can crop up in some HEMS operations.

OK. First let's consider departing from a rooftop helipad. As we have discussed in other posts, one way to perform these departures is to lift vertically, with the departure spot beneath the aircraft, to an altitude (perhaps 30 to 50 feet up), then to accelerate forward from this point in space. The logic of this technique is that if the aircraft loses half or all of it's power while hovering over the spot, it can return to the departure point. This takeoff technique resembles the "category A takeoff" as practiced in Europe, but in most cases pilots in America don't back up as per a real cat A during the climb. Backing up lets the pilot keep her eyes on the departure pad - but many of us hate to hover backwards.

This vertical technique was taught by Omniflight's chief pilot to me during Bell 230 transition training in 2004.. It was also taught years later by an Air Methods check airman during Astar transition training. It's a technique, and like any other it has good points and bad points. The bad point is that the aircraft is operated for a longer period of time in the "avoid" area of the height-velocity diagram, the "dead man's curve."




An example of one of these charts is here for your review . Most of these charts look basically the same, If you look, you can see that we are supposed to accelerate to - depending on aircraft and chart - 30 or 40 knots before climbing more than 10 or 20 feet above the surface. Now, looking at the chart, and imagining us flying off the edge of a roof-top pad so that instead of being 30 or 40 feet up we are now perhaps 150 feet up, one can see that as we do this, we go further up into the avoid area and remain there until we accelerate.



Probably for this reason, the FAA's Helicopter Flying Handbook recommends a level, accelerating departure, from a "pinnacle." For the purposes of this discussion, we can consider a roof-top pad a pinnacle. The technique is known as "airspeed over altitude."



From the FAA...



"Takeoff

A pinnacle takeoff is considered an airspeed over altitude

maneuver which can be made from the ground or from a

hover. Since pinnacles and ridgelines are generally higher

than the immediate surrounding terrain, gaining airspeed

on the takeoff is more important than gaining altitude. As

airspeed increases, the departure from the pinnacle is more

rapid and helicopter time in the “avoid” area of the height/

velocity decreases. [Figure 10-10] In addition to covering
unfavorable
terrain rapidly, a higher airspeed affords a more
favorable glide angle and thus contributes to the chances
of reaching a safe area in the event of a forced landing.
If a suitable forced landing area is not available, a higher
airspeed also permits a more effective flare prior to making an autorotative landing."

Are you confused yet? Why on earth would a company chief pilot or check airman teach a procedure that runs counter to the guidance from the FAA. Well, I think it has to do with different assessments of risk factors. If you fly over the edge of a rooftop pad at 5 feet and 5 knots, and the motor quits, you are going to be in a trick.

This actually happened to a pilot in the Gulf of Mexico recently. His motor blew up just as he was leaving the elevated pad of an offshore oil rig. Had he performed a vertical liftoff, and the motor had done the same thing - gone bang - he would have spread his skids on deck, and he would be probably be alive.

Here is a bit from the NTSB report on that event...

...About 1 to 2 minutes later, the witness observed the helicopter pull up into a 3 to 4-foot-high hover over the helipad and make a slight bearing change toward the east. He said that, at that point, everything was completely normal with the helicopter. The helicopter then moved forward and started to take off toward the east. The witness said as soon as the helicopter cleared the helipad's skirting, he saw a flash and a large (10-foot-high x 10-foot-wide) "poof " or " cloud " of white smoke come from directly under the main rotor blades near the exhaust section of the helicopter. This was followed by a loud, high-pitched, screeching noise, as if the engine were being revved up. The witness said this " poof " of smoke occurred when the helicopter was parallel to a flare boom that extended directly out from the platform and was positioned on the north side of the helipad. The helicopter then nosed over toward the water; cleared the helipad's skirting and did not strike the flare boom as it descended.

Click here to read that full report from the NTSB...


Let's change gears for a minute and consider approaches. That same HV chart applies on approaches, the airspeed and altitudes still matter. One large HEMS company directs it's pilot to make approaches such that the aircraft is in the avoid area for about 90 seconds every time they land off-airport. The descent down through the last 300 feet must be less than 200 feet-per-minute.

I wrote about this in another post


That company wants the pilots to use a technique that runs counter to what the FAA manual says (apparent rate of closure of a brisk walk) and the reason is that they are more concerned with vortex ring state or settling with power and/or wire strikes. And it's their helicopter, and their operating certificate, and they sign the front of the paycheck. So their pilots make these painfully slow approaches or they are shown the door.

So, when one pilot takes off one way, and another pilot takes off another way, who is correct? Well, as unsatisfying as this may sound, they may both be right. One may be following his own instinct, or company policy, or it may be the way his crew has asked him to fly. One guy may have had an engine quit on departure. The other guy may have lost a tail rotor at a high hover or perhaps he is just worried about that - and he wants speed on departure as quickly as possible for it's streamlining effects.

So in our humble opinion, what is the answer?

Just talk to each other. Is it so hard to have a calm and rational conversation with the people we work with that we instead get angry and huff off to our little corner of the internet to write angry spiteful things about each other? Are we so territorial that we can't share our opinions and ideas with people who may see things differently?

Sure we can. We are HEMS Professionals...


2 comments:

  1. Interesting 1958 US Army documentary on Helicopters:
    www.icineflix.com

    ReplyDelete
    Replies
    1. Thanks for stopping by and sharing the link. Found it on youtube as well and posting now. Surf's up!

      Delete

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