The Duncan Download Blog: Business Aviation Advice & Observations

How A WAAS (LPV) Approach Counteracts Temperature Effects

Posted by Diane Heiserman on Wed, Sep 05, 2012 @ 12:00 PM

Contributed by Gary Harpster, Avionics Sales Representative


A WAAS/LPV approach eliminates altitude errors caused by extreme temperatures.

The altimeter reading in an aircraft with Air Data Computers, displays the altitude based on barometric pressure.  Temperature plays a role in the accuracy of this information. When the air is cold, it is condensed and the altimeter reading will be less than the true altitude. Conversely, in hot weather the uncompensated altitude will bring the aircraft higher than the published alt constraint. That is why settings must be adjusted by the crew based on the readings provided by Air Traffic Control (ATC) or the controlling agency for the area they are flying in. This adjustment can be 100-300 feet depending on the temperature.

During an approach with WAAS/LPV, the initial vertical guidance is computed by the Flight Management System (FMS) based on the current altitude the aircraft believes it is flying at. At some point during the approach, the vertical guidance computed by the Air Data Computers will transition over to vertical guidance from GPS satellites. Once this transition occurs, the Air Data Computers are removed from the equation and the altitude error, caused by extreme temperatures is no longer a factor. With GPS, the descent is merely a mathematical equation based on current GPS altitude and selected three dimensional approach path.

Straight Talk Books

Duncan Aviation's free Straight Talk books are an aircraft operator's source for easy-to-understand information about WAAS/LPV and many other important topics in business aviation today. These publications are written by Duncan Aviation's very own aviation experts, and the authors are just a phone call away. Download your free copies at

Duncan Intelligence Live IA Seminar

Next Generation initiatives continue to become a reality in the aviation community. Get a more in depth look into the complicated subject of FANS at the next Duncan Intelligence Live IA Seminar. Steve Elofson, Duncan Aviation Avionics Sales Rep will be presenting his IA-approved class on FANS. Register now for this face-to-face forum discussion with industry experts and earn 8 hours of Inspector Authorization (IA) renewal credit.  

Gary Harpster is an Avionics Sales Representative at Duncan Aviation's Lincoln, NE, facility, specializing in the Hawker and Learjet airframe. His aviation career began in 1977.

Tags: Avionics Installation, WAAS, IA Renewal Events

FAA Flammability Testing Requirements for Business Aircraft

Posted by Diane Heiserman on Thu, May 17, 2012 @ 03:27 PM

 Contributed by Cliff Barker, Flammability Engineer

GIV Cabin Seat

In 1984 the FAA increased its flammability requirements beginning with the materials used for cabin seat cushions.

From 1981 - 1983, there were 277 transport category aircraft accidents in the United States. Of all the accidents that involved a post-crash fire, 34 were determined to be SURVIVABLE, yet nearly 600 passengers still suffered fatal injuries. In an effort to reduce the hazardous risks to passengers and crew aboard an aircraft during a SURVIVABLE accident, in 1984 the FAA began requiring certain materials used within the interior an aircraft to pass more stringent flammability requirements beginning with the materials used for seat cushions.

Today, all materials used in major repairs and alternation of an aircraft must past a series of FAA-approved flammability tests to be cleared for use. Although minor repairs/alterations do not require FAA approved test data, testing must still be provided to show that the proper testing was conducted for the material “As Installed” and that the results of these test are within their passing criteria

As a part Duncan Intelligence LIVE held May 23 in Battle Creek, MI, I will be leading an Inspector Authorization (IA) course on Flammability Testing that covers the FAA’s Flammability Regulations and how they are applied throughout the aircraft.

Duncan Intelligence LIVE

Duncan Intelligence LIVE is a free educational business aviation seminar, hosted by Duncan Aviation's Regional Managers. It is a face-to-face forum discussion with industry experts on hot industry topics as well as courses with Inspector Authorization (IA) renewal credit.

There is no cost for the event or meals and seating is limited. Come early the day before and enjoy an evening of golf and food. Click here to view all the course offerings and register for the event.

Cliff Barker is a Flammability Engineer at Duncan Aviation’sBattle Creek,MI, facility. He specializes in FAA Flammability Regulations. His aviation career began in 1978.

Tags: Regulations, Interior Refurbishment, IA Renewal Events


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