Weather Radar Usage Boeing question
 

Looking for help from the experts out there.....with regard in particular B757/767 radar's although the response may be of interest to other public transport drivers.

Under JAR and FAA ops it is mandatory for public transport aircraft to be FITTED with Weather Radar.

MEL's also include restrictions on aircraft flying with an INOP Radar.


I am currently flying for an unamed operator flying B757, B767 and there is a general 'acceptance' to fly with the radar turned off.

I am sure this is wrong but cannot place my finger on the ink that says so.......
My argument would be that it is a 'tool' that was introduced and made madatory on public a/c to enhance safety. With restrictions on a/c flying mentioned in the MEL I would argue that it should be selected ON for flight......

So.....can you help and/or provide answers to the questions below.


1. What actually happens when the Radar switch is first turned on ?

2. Is there any requirement/mandate when and where it must be used ?

3. How does it interact with the GPWS system ?

4. How is the GPWS system turned on ?

:ugh:

I'd have thought the 'how it works' would have been covered by the ground school.

SOP's and common sense would dictate when you use it!

To try and answer this query:
1) With modern radars, the modulator within the TxRx will start to fire within seconds of being switched on (unlike to old 'RCA' type which took an eternity).
2) Darn good idea to use ALL of the time while operating the A/C.
3) Assuming you have EGPWS fitted, PREDICTIVE Windshear Alert is generated by the radar. (Again, assuming that this is modern Bendix/Honywell kit). REACTIVE comes from the EGPWC.
4) GPS/EGPWS is running full time; there 'aint an On/Off switch. (Just Gear/Flap O/Ride switches in many installations).

Oops, I of couse meant GPWS, not GPS...:*

"general acceptance to fly with it off."

Can't understand that one. It's free; it doesn't cost the pilot a shilling for the meter, and could save you embarassment of explaining how some pax or C/A's came to be dancing on the ceiling. In severe clear skies I can understand it being off, but that is an airmanship decision. If you can't see where you are going to be in 5 mins then it should be on.

Hello,

About weather radar, the MEL for the airplanes I operate (A3xx) states the following : may be inoperative when weather reports indicate that thunderstorms or other potentially hazardous weather conditions, which can be detected by a weather radar, do not exist enroute(etc..)

Yes, see above. But before being a requirement it is a matter of common sense... I mean you use wxr to avoid bad weather... during daylight in cavok conditions you can leave it turned off.
Another great issue is knowing how to use wxr in a correct way: aircraft manufacturers often write about correct operations of airborne wxr in their training manuals and AOM and it is very important to know how that system is working in order to use it in the best way. Messing around with TS and Cbs can put you in very bad situations and must be avoided at all times. Wxr is a tool designed to avoid Cbs in a correct way, and for that it is important to review sometimes how a Cb works, and where you can fly and where you must not.
Anyway just my personal opinion:ok:

Bye!

First, let's look at the Collins or Bendix/Honeywell weather radar that has been equipped on the 75/76 since their beginning 1982. The devices are solid state, so self-test and antenna synchronization takes only a few seconds. The transceiver operates to detect rainfall and precipitation related turbulence only when at least one pilot has selected WXR display.

2. If you can dispatch radar inop when no TS are predicted, then having it energized when no TS visible makes no sense. Flight at night is another matter.

3. Weather radar is standalone, and not connected to GPWS.

4. GPWS is on all the time. EGPWS, or the generic TAWS, Terrain Alert and Warning System is on all the time, too.

Predictive Windshear Weather Radar, or more correctly, Forward Looking Windshear Weather Radar, is independent from GPWS or TAWS, and became available in 1995, when Windshear detection and warning was mandated in the US. It is energized when there is oil pressure to one engine and Transponder On, meaning the plane has left the gate, scanning the sky for windshear events, although the display may be off. It operates automatically to about 2300 feet on departure, sharing the standard rainfall detection task if the pilot has engaged his weather radar display.

Likewise on the approach, the FLWS turns on at 2300 feet, providing alerts and warnings as needed, regardless whether the pilot has turned on his display of rainfall and turbulence detection.

GB

Greetings,
Weather Radar have to be ON in certain region (military conficts close by) so that your plane will be identified as civilian...
Now leaving it on all the time is NOGOODLAA, because the antenna will deteriorate and side lobes will be an issue.
So what is the best? If your flight is well above the tropopause then switch it off, otherwise look at your significant weather chart to see where it is needed due to weather, and mark it on your Flight plan paper copy, (so that you will not forget it) and buzz off.
As far as I am concerned I leave it ON. :ok:

Thanks for all who have replied thus far........

I tried asking the question in a way not to prempt or lead an answer......

Let me further say....and reply without directing to any one individual.

Most people are aware of what is taught in ground school and how things work ina general way. Just need to look at Mr Boeing Manuals to see how much these days has been removed and no longer covered.

As far as SOP's and common sense go, I have seen examples of where both are somewhat lacking.....

I am aware that MEL;s have placed restrictions on the type of flights made and the despatch of a INOP radar. BUT......
the MEL mandates when despatch may be made NOT that it has to be used !

I am aware that there is a notam affecting flights into 'sensitive' area's whereby you are REQUIRED to use it......or risk being shot down.

Looking at EGPWS I know that when you turn the thing on (RADAR) it automatically sweeps and scans for Windshear, which is great as you line up just before takeoff........

BUT if GPWS is 'ON' all the time then when is it first powered'......and how or rather what activates it.........if as mentioned above when oil pressure is indicating that and engine is up and running and 'left the gate' then what is the actual process involved........

ALSO if EGPWS ....windshear detection is first scanned when the RADAR is first switched on then how does the system actually work......
Vague recall about mode 7 of EGPWS......(currently downroute & no access to loads of books..etc etc)

Thus I come back to the original questions.........

Is it written in black and white where I can point my finger and say........

I knew it would potentially open up a can.....

By the way I do fly with it on and utilise tilt/range to interrogate wx ahead but I'll be darned if I can find the answers anywhere thus far....!

Greetings
Go back to the root, use the Pilots Guide published by the company who made your Radar. :ok:

I must not have been clear in my prior post, BGA. . GPWS, Ground Proximity Warning System and EGPWS, Enhanced GPWS are entirely unrelated to FLW, Forward Looking Windshear, except for priority of alerts and warnings.

The startup logic for FLW when leaving the gate: oil pressure on either engine, transponder ON and less than 2300' radio altitude. It begins with a self test, and then scans for microbursts. Alerts and warnings are inhibited above 100 knots and below 50' radio altitude. Once above 2300' radalt, it shuts off.

Crossing 2300' radio altitude on descent. turns it on again, of course.

I have not heard of WXR being used as IFF. Sounds bogus to me. The beam is only in the forward hemisphere. and not necessarily aimed at ground installations. I have seen spokes on the display that point to military facilities, however, due to ground based radars on the same X-band frequency.

GB

Greetings
It is quicker to state that it is Bogus, then to do so research on it,:} it goes back to the period when an A300 Airbus IranAir was shoot down in the Persian Gulf, Civilian weather radar have a different signature from military tracking Radar.

It's somewhat technical, but the Iran Air shootdown occurred when the USN ship's IFF confused the 6400 feet Mode C altitude reply from the A300 with a discreet Mode A code often used by the Iran AF.

Meanwhile, airliner weather radars have evolved from 60KW peak power to 150w peak power in a scanning pencil beam. That's hardly comforting to think a military would depend on that to distinguish a transiting airliner from an enemy intruder.

Besides, the KC-10A tanker and other USAF planes use commercial WX radar..

Greetings, I never stated that they rely only on that to identify.....

Sounds a bit dodgy... What if the aircraft had to start an engine at the gate due to maintenance reasons.

Our 747-400 books say that takeoff thrust achieved on #2 or #3 engine will activate predictive windshear. This is more likely to be an rpm value, rather than oil pressure. Haven't checked our 767 manuals yet.

Rgds.
NSEU

Greetings,
As Windshear was on the top ten list, authorities have asked airframers to wire the system in such way that predictive windshear will be available at takeoff, even if WXR Radar is switched off, so all sorts all mods had to be done, from oil pressure during engine start (I believe B737 is the case) to takeoff thrust and 80kts.
the configuration is more related to what could have been done to implement the requirement, this is why you will hear different stories.:ok:

Hi BGA,

If I understand your point, you are talking about general company policies on use of weather radar, right? You might have radar on required for takeoff everytime as per SOP, but after that having it on or off could be left upon crew discretion if there is no significant weather. What is mandatory is to use radar when there is weather ahead and making a good assessment of the situation.

Bye !

Modern weather radar units still require the use of some mechanical parts. These include gyros; jack-screws; and various bearings, seals and lubricants.


In simple terms, it's cold outside. Somethings as cold as -60. I doesn't take a rocket inventor to understand what happens when mechanical objects are subjected to that level of cold; then snapped on and expected to work without impediment.


Most people shut these things off out of fear of the radiation exposure. However, (and I'll happily provide the reference document) the level of radiation from that modern aircraft radar, is about HALF that of your typical modern Hand-phone.


Personally - like someone else stated earlier - I also believe:

1. I costs nothing to use,
2. Using it properly – even in clear conditions – continually reminds you that it IS WORKING, and
3. There are NO adverse effects to using it.

Your company SOP should always prevail, but given the overall - and obvious - lack of knowledge with WX Radar systems, it's no surprise that so many companies simply don't address its regular use in their SOP.


Cheers

Corrections
 

OK, I checked a Lamm diagram for FLW, and retrofit installation is one engine running (oil pressure discrete), transponder ON, and less than 2300 feet radio altitude.

You want the system working before taking the runway for takeoff.

Alert Inhibits:
*Above 100 knots and Below 50 feet on takeoff
*Above 1200 feet radio altitude
*Targets Beyond Touchdown Zone on Approach

I'll edit my prior post. Sorry for the confusion.



GB

As a radar engineer I often read radar-related threads around here and observe the comments with much interest. I'm not a Boeing driver (light singles only) so I cannot comment on SOPs for radar use, however there are a few points I'd like to comment on.

A point well mentioned, as the effects of cold are also present on the electronic components. Thermal shock damages components and is the main cause of failure. Cold-soaking a radar at -40C for a period of time and then powering it on (therefore heating it up) will subject the components to significant thermal stress and will very quickly cause failure. If the unit is powered-on on the ground, e.g. when lining up on the runway, the circuitry will already be warmed up and therefore the effect of extreme cold at altitude will not stress the circuitry as much. Thermal stability is an important consideration with most electronic systems, applying no less to radar.

Not sure about the comparison with the mobile phone power but sitting behind a transmitting radar will NOT have any affect on you. The microwave energy is radiating away from you, and you are sitting behind it. Nothing to worry about. A lot of people are scared of radar and RF tarnsmissions and their affects on health. Much interesting work has been published on the subject and is readily available via a search engine but the fact is it will have no affect on you, unless you are daft enough to stand in front of a transmitting antenna, in which case you will feel a bit warm and have your balls sizzled. :suspect:

My take on it - if it's there, use it. :)

Smithy