Handling Heat


Excellent article by Tom Turner in Julys issue (“Hot And High How-To”) but a couple of things come to mind. First, in the sidebar Cruise Considerations, you infer that a high density altitude decreases the available amount of oxygen for breathing. This is technically true, but the difference is so small it is hardly worth considering.

Obviously, if one feels the need for it oxygen should be taken regardless of altitude, density or otherwise. A pulse oximeter is a huge help here, and the basic

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guideline is to maintain a saturation level that is within 10 percent of sea level saturation to avoid judgment impairment.

Dr. Jack Hastings, former author of the American Bonanza Societys Aeromedical column, and a past president of the group, was kind enough to research and answer my question concerning density altitude and human saturation. Briefly stated, he said that oxygen saturation in the human body is dependant upon the “partial pressure” of oxygen in the atmosphere to create the osmotic exchange in the lungs. That partial pressure is only slightly affected by density altitude, and therefore insignificant.

Second, Mr. Turner makes reference to some EGT values for setting power. I believe most aircraft engines are set up to produce their sea level rated horsepower at a fuel flow resulting in EGT that is 150 to 200 degrees rich of peak. This provides optimal cooling at high power and low airflow (takeoff) conditions. A good target value for cooling is 1250 to 1350 degrees F, but is well rich of the “best power” value of 75 to 80 degrees F. rich of peak EGT.

I believe something in the low- to mid-1400s would be closer to “best power” since, even at 10,000 feet, full power peak EGT is probably around 1500 degrees F in the TCM IO-550. At those altitudes a normally aspirated engine isnt producing enough power to hurt it no matter where you set the mixture.

A final thought is that when operating off of high density altitude airports, one must adjust their performance expectations, and be very gentle with pitch control so as not to further degrade already marginal performance. It just aint gonna fly like it did at sea level

As always, kudos on putting out such informative articles.

Jim Piper,
Palos Verdes, Calif.

Thanks for the feedback. The only quibble we might have involves takeoff EGT values. We prefer our EGTs in the 1200-to-1300-degree F range for takeoffs. This can require high-than-book fuel flow. Using such values helps ensure the cylinders remain cool, even at full power and low airspeed, in an area of the output curve where power remains relatively unaffected.

In other words, well run some more fuel through the engine at takeoff to keep things cool while not giving up much-if any-power loss. If things are so tight we need the extra power, well reconsider the takeoff by lightening the load or getting up early the next morning.

Plan Continuation Bias

I just finished reading Rick Durdens article, “Going Below Minimums” (July) and was

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really intrigued by the concept of “plan continuation bias.” As an instrument-rated pilot I recognize the issue clearly, but I am also responsible for our quality system within our design centers and see engineering project managers who suffer from the same malady: design projects that move inexorably onward when all verification and validation protocols say we have a problem with the project. Great article for me to think about in both arenas.

Joseph Sener,
Via e-mail

More On MOAs

I am disturbed by the attitude expressed in your May 2008 article, “The MOA Mess”: “A recent episode involving two civilian airplanes in an active military operations area should be a reminder there are times we really shouldnt be there.”

This is wrong!

The civilian aircraft had a perfect legal right to be where they were. There was no valid reason for an intercept. And if it wasnt an intercept, isnt it improper to fly close formation without the other aircrafts knowledge and consent? How close does an F-16 pilot have to be to “establish visual contact” with a PC-12? Multiple approaches? 15 or 20 seconds close formation? Was the purpose of this “controlled maneuver to ensure that neither aircraft was placed in any danger?” Major Gilloon must have had a hard time keeping a straight face during that distortion.

This seems more appropriate conduct for a first-solo high school kid than a well-trained, fairly senior military officer who is training to be entrusted with $50 to $250M aircraft capable of causing more destruction than anything short of a nuclear missile. Its especially disappointing that the officer who conducted the

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“intercept” (your word) was the training missions lead (apparently senior officer). And I strongly question the capability and honesty of Major Gilloon. Sounds like a stonewall-it-until-it-goes-away public affairs approach.

Morris Holmes,
Via e-mail

Since we published that article, AOPA has obtained a video of the radar returns and radio calls involving the F-16, and its intercept of the PC-12 and the Beech Premier business jet. The additional evidence AOPA obtained definitely casts the F-16 pilots actions in a light different from that portrayed by the Luke Air Force Base public information officer, Maj. Gilloon.

According to AOPA, the “F-16 pilot, based out of Luke Air Force Base, was reprimanded. Luke officials have told AOPA that they will alter their local training program to avoid this type of encounter in the future.” Lets hope so.

INFO, Please

Februarys article on transitioning from a certified airplane to a light sport aircraft (LSA) (“Safe LSA Transitions”) included several tantalizing photos. One caught my eye in particular and was referenced only in a photo caption: the Corsrio. Do you have additional data or contact information on it?

Kelley Mala
Miami, Fla.

The Corsrio is manufactured in Brazil by Microleve (www.microleve.com.br) and exclusively imported into the U.S. by Sportair Aviation (www.sportairaviation.com) of St. Petersburg, Fla. Base price for the complete aircraft, including a 100-hp Rotax 912S engine and a three-blade prop, but not including flight instrumentation or avionics, is $47,500, according to Sportairs Web site. Itll come needing the wings and engine installed to the fuselage.

Another amphibious LSA, the ICON Aircraft A5, is under development and recently completed its first flight. A significant feature is foldable wings, allowing the aircraft to be transported by trailer.


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