Page 5 - Twin and Turbine September 2017

Airmail
IRadar Feedback
have to drop a line to say thanks to Twin & Turbine and Joe Ratterman for two terrific articles about onboard radar. (“Look Up Look Down...Look Out!” July 2017 & Beam Me Up
Scotty!” August 2017) I’ve been flying with onboard radars for many years, but until now I never understood how to get optimal utility from my radar. Joe’s article makes it easy to understand the geometry and the math. Articles like this are potential life savers. Thanks again.
James (Jim) Kabrajee Toronto, Ontario
While the information on use of onboard radar is well presented and appreciated, there is more to discuss regarding the two images in “Beam Me Up Scotty.”
As mentioned last month, one must mentally shift position of NEXRAD images in the direction of movement, about 5 miles, which would, again, properly locate the NEXRAD storm. Of the 14 factors a pilot needs to consider in evaluating thunderstorms, true size and true intensity are most important and most accurate if you are receiving NEXRAD composite images, not base images. (I will be discussing these 14 factors in the near future.) In this instance, the intensity of the NEXRAD image is uncharacteristically low compared to radar...unless it is a base image. The government mandates labeling of images as either base or composite. There is no such label on this image.
For years, numerous NEXRAD receivers were sold that only received base images. Therefore, it is imperative you know the type of images you are receiving. In most cases, without an operational issue such as a NEXRAD site down for maintenance, datalink composite NEXRAD images identify the correct size and intensity of storms outside and inside the operational range of radar (40-50 miles).
This NEXRAD image identifies the cell as part of a line of storms extending off the top of the screen, not seen on the radar image. Not displayed on NEXRAD is the radar’s false image of the city of Wichita. While there are some circumstances in which radar may display the situation better than NEXRAD, I have hundreds of examples the other way around. Of the last 14 fatal thunderstorm related commercial accidents, 13 would not have occurred if the pilots had NEXRAD on board and the 14th one would have given the crew much better odds of survival.
Attaching the terms “strategic versus tactical” to each piece of equipment should be dropped from our vocabulary. I use both for all situations. As I have said before, using only radar for close-in work without the aid of NEXRAD can be a critical mistake.
Dr. David A Strahle Flint, MI
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September 2017
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