A few to ponder

[CV Donator]

I have a interview coming up and have a few questions.

1. What is best for stopping on a dry runway initially, reverse or brakes. I know on a wet runway it would be a combination of reversers and speed brakes.

2. What is a macroburst

3. What is RAIM in reference to GPS

4. Why can't a wx radar see past the first line of thunderstorms in a line of thunderstorms.

Anyway back to those old Oxford notes in the meantime. Many thanks.

[Down Three Greens]

1. Brakes....the simple answer. Can't post diagrams but I hope this helps.

http://www.flightsafety.org/alar/alar_bn8-4-braking.pdf

2. Macroburst

A downburst is a strong downdraft which includes an outburst of potentially damaging winds on or near the ground. If the diameter of the downburst is less than 2.5 miles, it is called a microburst.

A macroburst is a strong downdraft, of over 2.5 miles in diameter.

3. RAIM

RAIM is essentially a fault detection scheme that is applied to the GPS measurments (pseudorange). Traditional RAIM uses fault detection only (FD) however newer GPS receivers incorporate Fault Detection and Exclusion (FDE) which enables them to continue to operate in the presence of a GPS failure. FD compares position and time information derived from combinations of four satellites in a set of five satellites (or four satellites and an altimeter input). In this way, a faulty satellite can be detected and the FMS provided with a warning that the position information should no longer be used for navigation. With six or more visible satellites, FDE will not only detect a faulty satellite but it will also remove it from the navigational solution and continue to provide FDE or FD with the remaining satellites.

4. ATTENUATION

An extremely important phenomenon for the pilot to understand is that of attenuation. When a radar pulse is transmitted into the atmosphere, it is progressively absorbed and scattered so that it loses its ability to return to the antenna. This attenuation or weakening of the radar pulse is caused by two primary sources: distance and precipitation.

Attenuation because of distance is due to the fact that the radar energy leaving the antenna is inversely proportional to the square of the distance. For example, the reflected radar energy from a target 60 miles away will be one-fourth of the reflected energy from a target 30 miles away.

Attenuation due to precipitation is far more intense and is less predictable. Since some of the beam energy is absorbed by precipitation, the beam may not reach completely through the area of precipitation. If the beam has been fully attenuated, the radar display will show a "radar shadow" which appears as an end to the precipitation when, in fact, the heavy rain may extend for many more miles.

New weather radars have software processing such as

Path Attenuation Compensation and Alert (PAC Alert): Compensation for attenuation due to intervening weather is provided within 80 NM of the aircraft. When compensation limits are exceeded a yellow PAC Alert bar is displayed to warn the flight crew of an area of radar shadow

Extra info - http://www.rockwellcollins.com/ecat/at/Whitepapers/WXR2100WP.pdf

Best of luck

DTG

[CaptSkipper]

Nice one D3G's. Helpfull info which i'm sure many of us have forgotten.
cheers :ok: !

[Old Smokey]

Down Three Greens,

A very nice piece of work indeed, and in record time. I think that in all of PPRune's pages that gets the record for 'One reply says it all'. Had I been the original question poser, I would have been one satisfied customer:ok:

Regards,

Old Smokey

[Down Three Greens]

Glad I could help.

Regards

DTG

[plain-plane]

D3G
you know, had this been the olympics, WADA would be raiding your hotel room right about now- hope you dont have too many Austrian friends.

truely impressed :ok:

[hawk37]

Just my $.02

RAIM stands for Receiver Autonomous Integrity Monitoring.

Re question 1,
"1. What is best for stopping on a dry runway initially, reverse or brakes. I know on a wet runway it would be a combination of reversers and speed brakes."

Perhaps I don't really understand the question . Dry or wet, brakes provide the best deceleration, if used.

[CV Donator]

Can I echo the sentiments expressed earlier; thanks very much for the reply. It is useful to have insights such as yours.