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ms80831
07-23-2011, 07:18 PM
Guard trains helicopter pilots to cope with thin mountain air
Colorado Springs Gazette

2011-07-23

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EAGLE • Maneuvering a lithe OH-58 Kiowa above a 12,000-foot peak, Maj. Tony Somogyi does math in his head.

The aircraft weighs this much, his passengers add another 400 pounds. The fuel adds a few hundred pounds more. Meanwhile, the altitude saps power from his turbine engine, and the heat of the day makes it even weaker. The trick is figuring out how much engine power is available and whether he can land and take off again without crashing.

“It’s all about power management,” said the Iraq War veteran who teaches at the Colorado National Guard’s mountain flying school in Eagle.

The school teaches lowland pilots that, in Colorado’s high country, the Army’s strongest helicopters become the Dodge K-cars of the sky. More brick than bird, their turbine engines wheeze from lack of oxygen and their rotor blades can’t get a grip in the thin air. High temperatures further thin the air, making the altitude problem worse.

“What do you have in common with your aircraft?” Chief Warrant Officer Anders Nielsen asked a room full of Army pilots last week during ground school in Eagle. “You both suck at altitude.”

The lesson has never been more important. In Afghanistan, American helicopters routinely fly and land at altitudes above 10,000 feet, a height where helicopters seldom venture.

Mother Nature is the biggest threat to helicopters in the mountainous war zone, destroying four aircraft for every one shot down by the Taliban. One recent example: The helicopter crash on the secret raid to kill terrorist leader Osama bin Laden in Pakistan was reportedly caused by loss of lift at altitude rather than enemy fire, although details have not been released.

“It’s just sickening that we are killing ourselves 78 percent of the time,” Nielsen told his students.

Helicopters are creatures of low altitudes, generally hugging the ground even at sea level.

The all-time altitude record was set at just over 40,000 feet in 1972 in an effort that nearly killed the French crew when the engine flamed out. That’s a height where airline passengers routinely whiz through the sky.

When the Colorado National Guard began teaching pilots how to deal with the thin air of the Rockies a quarter century ago, only an elite few in the military took the risk.

In Afghanistan, the Army can’t avoid high-altitude helicopter work. The country has few roads, so helicopters take the place of trucks to resupply troops and to haul units to patrol bases. Attack helicopters are crucial, too. They provide close-in defense from insurgent attack, and in a nation where every civilian casualty can cause a riot, the pinpoint helicopter firepower is preferable to lumbering bombers that can take out whole villages.

Now, the small National Guard school in Eagle and a larger program at Fort Carson are aimed at cutting the number of crashes in Afghanistan. And the mountainous terrain of the Pikes Peak region was one of the top reasons that the Pentagon announced this year that it will put a 2,800-soldier Army aviation brigade in Colorado Springs.

The school in Eagle, across the regional airport from terminals that welcome sleek private jets, is considered to be the most elite in the country. It’s called the High Altitude Army Aviation Training Site.

Training 425 pilots a year, the program has been all but copied by the active-duty Army to train crews for Afghan flying. An aviation brigade from Hawaii is heading to Fort Carson in a few weeks to be trained.

“You have to understand yourself, understand your aircraft and understand your environment,” said Maj. Josh Day, who leads a staff of 26 that conducts the training with seven aging National Guard choppers.

The National Guard uses land under an agreement with the federal Bureau of Land Management and the U.S. Forest Service. The deal is reviewed annually and the pilots say they’re sticklers for following rules, staying clear of wildlife and campers and even grounding the program during hunting season.

At more than 3,000 sorties per year, the flying program must be careful to avoid annoying neighbors in Eagle who came to the mountains for peace and serenity.

“We try to fly neighborly,” Somogyi said.

The training is more science class than Top Gun. It starts in a classroom where pilots learn the math of how high temperatures and thin air cause crashes.

“Numbers can kill,” Nielsen told students.

Then it’s up to the mountains to understand wind in a new way. Most people see wind as a horizontal force; in the mountains, wind moves in three dimensions, and a down draft on the backside of a ridge can slam a helicopter into the trees like an invisible hand.

The answer to the wind is engine power. Helicopters like the Black Hawk, designed to haul troops and sling-loaded trucks across the battlefield, usually have the horsepower to get out of trouble easily. Not at altitude.

“This is the first time I’ve noticed there’s a limit to my torque,” said Chief Warrant Officer Sean McKay, a student from the Hawaii-based 25th Infantry Division who was getting some advance training in Eagle before the unit heads to Carson. He had spent the morning flying in the mountains, practicing landing and taking off on 10,000-foot ridges.

“You can definitely see the power difference,” said Chief Warrant Officer Brian Hill, another 25th Division student.

Hill and McKay are heading to Afghanistan this year to fly in combat.

“It’s good training,” Hill said.

But measuring the results of training is elusive, Day said.

“There’s no statistic for crashes that are avoided.”

StanFoster
07-24-2011, 05:35 AM
Mark- Thanks for that interesting post. The other day I was flying with 98 degrees, high humidity, but starting off at only 770 feet. My density altitude at takeoff was 3800 ft. This is my worst condition I could ever fly in, unless of course I few at 100 degrees. But my worst is still 1200 feet less than what you have on a standard day, let alone when you also are in the 90"s! I have plenty of reserve as the Helicycle has flown over 12000 ft. Besides the engine loosing power at higher density altitudes, its the fact that the rotorblades have to satisfy the lift equation. There is less molecules to accelerate, so to have the same lift, the fewer molecules have to be accelerated more, which goes up with the square of the speed. That plus the rotor blades are at a higher angle of attack, their L/D ratio lowers and more drag results from these higher angle blades trying to accelerate fewer molecules to a higher speed. Interesting topic to me, even though my highest density altiitude I probably will ever see in my helicopter on my worst day will probably never exceed 7000 ft. I would have to fly over 3000 ft high on a 100 degree day to get that high, and I seldom fly over 1000 ft. On my cross countr to Mentone, I will cruise around 2000 ft. Stan

ms80831
07-24-2011, 11:49 AM
Mark- Thanks for that interesting post. ..... I would have to fly over 3000 ft high on a 100 degree day to get that high, and I seldom fly over 1000 ft. On my cross countr(y) to Mentone, I will cruise around 2000 ft. Stan

Stan

Yesterday when Todd and I took off , the AWOS was reporting density altitude 9 thousand six hundred, at 8:45 am ! By noon it was over 10K.

I have been at this airport for over 27 years, and actively in the airport management for almost 25 years. It never ceases to amaze me how little most pilots who move or visit here really understand about density altitude. Sometimes that lack of understanding has a tragic result.

You obviously get it. Consider yourself one of the few.

Helicopters and Gyros don't stall, but they most defiantly do settle with full power under the right (wrong) conditions.

But until a pilot actually experiences it, ....nothing sinks home the lesson like barley clearing the takeoff you zoomed over in the same aircraft, same weight, just last week. It is a sobering eye opener. (It can be a bladder opener too depending on how close to the fence/tree/building you get.)

Mark Shook
Vice President /MLAA
(The Airport Authority at Meadow Lake Airport.)
www.kFLY.org

steve5248
07-24-2011, 03:01 PM
I have a rookie question for you. Are rotor wing aircraft, specifically autogyros, more susceptible to density altitude problems than fixed wings?

RotorTom
07-24-2011, 08:17 PM
I flew my 480B last week at 10K density. Whew! Not only do you have aerodynamic challenges, but the "TOT" is the real limiting factor. It takes no time at all to get to "red line".

Also ... I was doing a pinnacle and as I was descending I noticed that as I was pulling collective, the sink rate did not slow much, even back pressure kept me sinking. I knew that I would have an unhappy result at the bottom ... so I made a shallow right turn downslope ... giving back power and gaining airspeed along the terrain.

Next try was way better with a much shallower approach.

There is so much more to flying up here than cyclic/collective ... the elevation makes you keenly aware of limitations that some pilots never experience.

Fly Army
07-25-2011, 05:36 AM
I was a member of the Eagle unit from 93 to 97, a lot of good friends still there.

ms80831
07-25-2011, 12:05 PM
I have a rookie question for you. Are rotor wing aircraft, specifically autogyros, more susceptible to density altitude problems than fixed wings?

Yes somewhat.

Most G/A Fixed wing aircraft have major performance issues operating at 10K DA also. That is near the service ceiling of many low power 2 and 4 seat aircraft at gross weight.

Rotorcraft have related issues of lower engine power and less dense thinner air not allowing the rotors to generate enough lift at red line RPM.

I changed my rotor blades from the 8.2 meter (26.9 ft) standard blades to the 8.8meter (28.8 ft.) aircopter blades for that reason.

Mark

ms80831
07-25-2011, 12:12 PM
I flew my 480B last week at 10K density. Whew! Not only do you have aerodynamic challenges, but the "TOT" is the real limiting factor. It takes no time at all to get to "red line"...........
There is so much more to flying up here than cyclic/collective ... the elevation makes you keenly aware of limitations that some pilots never experience.

Tom

These hot summer days take skill and judgment to fly most aircraft near the margins. Rotorcraft have special issues. Temps, Rotor RPM, etc.

BTW, Todd and I visited FTG last sat. We saw Dr. Clem, Mark and Dick. I guess you are mostly at APA now. I visit there often. What hangar are you in?

When do I get a ride in the new Enstrom? Just call, and I will have your helipad ready out front here at FLY.

Mark