Weather Radar - P-5530117

JOINT ADVANCED MULTI-ENGINE T-44A

levers. There are a few minor differences in right seat instrumentation (turn and slip indicator in a

different location, radalt is on the left panel), but your instrument crosscheck will be very similar.

Another difference is the visual sight picture when landing the aircraft; when new to the right seat,

pilots tend to land right of centerline.

Jeppesen Approaches. When flying an Air Force aircraft, you are permitted to use any NIMA (DoD)

or NOAA (FAA) publication. However, you may often fly into locations where there are no such

products available. Jeppesen products will frequently be used. Jeppesen is a quality company and

publishes quality products, but it is imperative to remember Jeppesen does not design or flight check

any procedure and Jeppesen has no authority to alter, modify, add to, or subtract from any flight

procedure prescribed by a governing authority. They simply publish procedures in a standardized

format. Because many of these governing authorities (countries) do not use the same standards we do

in designing instrument procedures, any non-NIMA or non-NOAA product must be approved by your

MAJCOM TERPs office before it can be used. Also, to legally fly with Jepps you will need to have

"official training" (a class on the use of Jeppesen products) and you need a complete set of documents,

including: the index, glossary, legend, chart NOTAMs, briefing bulletins, approaches, departures, and

field diagrams. Simply getting a faxed "approved" approach from a MAJCOM isn't good enough.

The approved use of any Jepps material is a one-time waiver.

F. Weather Radar.

The weather radar installed in the T-44 is a type of primary radar that can detect water drops. It cannot

detect air currents, turbulence, windshear, hail, or the fact that IMC exists, but it can warn you of the

possibility of these phenomena, since they are associated with cumulonimbus clouds, which do contain

large water drops. Large water drops reflect the radar beam transmitted from the airplane, and this

reflected signal is shown on the radarscope in the cockpit as a radar echo. Not all storm cells

containing large drops of water will be detected initially, since nearer cells may mask the presence of

more distant cells. Any storm cells strong enough to cause a radar echo should be avoided by at least

20 miles.

Attenuation. In the absence of very strong storms, radar will normally be capable of pointing out

precipitation well in advance of the aircraft because some of the electrical energy passes through to be

reflected by another rain area up ahead. But imagine a big storm straight ahead producing so much

rain all of the radar's energy is reflected back to the antenna. You would see a very bright echo, but

what you would not see is the big storm lurking on the other side. This characteristic is called

"attenuation" or "radar shadows." Just knowing attenuation exists should make it clear that you must

have some idea of the extent and severity of a weather system before putting all your weather

avoidance trust in what you see on the scope.

Radar Beam Anatomy. In the T-44 we have a 12" circular radar dish and this corresponds to a beam

width of 8. The larger the radar dish, the smaller the beam width. The smaller the beam width, the

more detail on the scope. Really good radar systems have beam widths of 3 or less. The point is we

have a limited capability. Because of characteristics that result from having a larger beam width, we

have to be much closer to the storm system to receive useful information.

Interpretation. There is a great deal of interpretation required of the pilot to extract useful, safe

information from the weather radar display. It is much more than a turn-it-on-and-take-a-look system

because the picture changes remarkably with range selection, antenna tilt, airplane altitude and attitude,

and storm characteristics. One of the limitations of radar is that when it is used as a go/no-go warning

device, it has a high false-alarm rate. Just because you have flown through a storm before that looked

just like the one you see now on the radar scope, doesn't mean you can safely do it again.

Weather Avoidance. Wise pilots avoid threatening weather (heavy precipitation and/or potential

turbulence) showing up on the equipment they have to work with. The key word in the last sentence is

avoid. They haven't yet built a weather detection system good enough to pick your way through a

squall line or to decide with confidence which of those storms up ahead is safe to penetrate. There is

always another route or another day.

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RADIO INSTRUMENTS STAGE