wx radar off inflite

[zeus_737]

I have a question. We fly the 320 family and we have some ol skool pilots who believe tht switchin off the radar above 10000' when wx is clear is a good idea.
is there any logic to it.And is it documented anywhere?

And is there any safe gaurd against the microwaves emitted from the radar in regards to flite creW health?

[Loose rivets]

Look at it from the other point of view...is there any reason to leave it on?

[helopat]

Weather radar points forward. You know this. Does that mean its safe? Who the heck knows.

What I believe is this...if you're worried about wx radar and health issues, you should also be worrying about the affect on your body of all the other electro magnetic thingeys we deal with in aviation and in everyday life. All those wire bundles under the floor in the aircraft...lovely electrical fields! Your mobile phone? Hope you don't get brain cancer (or, for that matter, testicular cancer from having it in your pocket).

I can't really see any reason to turn it off in flight...what little danger there is would be if you were directly in front of it and, at altitude, thats not real likely.

At the end of the day, if you want to turn it off in flight if the weather is nice,and it doesn't violate your ops manual, fill your boots.

(And before you say, 'what does he know about wx radar', my helo has weather radar...I just don't use it at 30,000').

HP

[IRRenewal]

wx radar and safety (http://hps.org/publicinformation/ate/q315.html)

If it is safe outside the A/C, I'd be very surprised if it isn't safe inside the aircraft.

[tired]

The thing about switching it off is that you'll probably forget that it's off when you need it. Maybe not a problem on short haul, but on long haul how sure are that you'll remember that it's off when you're looking at those nice fluffy clouds 10 hours later?

"Radar's not showing anything serious in this lot, we'll just nip straight through"!

[FHA]

These modern digital radars barely emit any more power than the HF and of course the signal is highly directional.
The old-school analogue radars could output at 10kw+ if I remember rightly. The key to reducing the output was processing power in the T/R.

Come to think of it, ex-Phantom crews do seem to glow in the dark..........

[Meikleour]

Many moons ago we had a new Fleet captain who advocated this procedure. However it was dropped after it was found that condensation on the scanner array gimbals was freezing in flight and making the weather radar unusable when switched on after a period! Some things just keep coming around.

[Centaurus]

I recall many years ago writing to the Bendix radar people on the same question. They replied that if you don't need the radar then switch it off. Saves maintenance costs, they said.

[wiggy]

There are some parts of the world ( e.g. The Gulf) where for all sorts of reasons it might be a very good idea to keep the darn thing on and radiating...

[tom775257]

Personally with electronics, for me, they always seem to fail being switched on or off. Why push your luck switching these on or off in flight when not necessary. They are certainly useful in the terminal area!

It is like the captains who tell me 'no' when I ask for wing anti-ice on (A320)when I see ice on the icing indicator. I'm told no, on the 737 we had to wait until you could see ice on the wing. Yes, you are not flying a f****** 737 you are flying an A320 with wing anti-ice/de-ice and as per Airbus instructions put it on at visible icing on the indicator!

[Denti]

Funny enough having EGPWS on at all times at least on one side is mandatory, radar is still optional. But thats shorthaul operation which might differ quite a lot from longhaul.

[SmokeAndNoise]

Denti:

EGPWS doesn't emit so I don't see the connection to this discussion?

IRRenewal:

Thanks for the informative link. It seems to mainly focus on ground crew though. And consider this from the article:...never to place any part of the body in region of the antenna and the feed horn......Doppler X-Band (9300 – 9500 MHz) transmitter with a nominal output of a few hundred watts of microwave power....We are sitting close to the antenna which is basically a microwave oven.
I know microwave ovens are only dangerous to domestic animals in the States (:}) but how would you feel about spending 8 hours a day 2 meters from one while it buzzes away at home?

Also, personally I have never experienced a radar not coming on again after being switched off in flight but I might have been lucky.

I say turn it on when you need it.

SAN

[No_Speed_Restriction]

If flying to an area with possible military activity then it is recommended to fly with your weather radar on.

[SEV]

I think that wx radar is quite important instrument to help pilots to be aware of situation. I think that switch it off is really a bad idea for many many reasons.Somebody swtch off the gps because sattellites has radiation???

[G-SPOTs Lost]

We use it on as a sop as wx radar txmittal can apparently help identify you as a civvie aircraft, introduced after 9/11 and invaluable when operating in the less civilised areas of the world or close to unfreindly borders

[Meikleour]

Ref: Stator Vane

Just because you have not come across a problem does not mean that it is not valid. The fleet in question was the B747 classic during the eighties whilst being operated in the Far East envirnoment where the ground level humidity was very high. The procedure was dropped because of this problem and didn`t occur with the scanner operating. As an aside to this, excessive water comtamination collecting on the walls of large empty fuel tanks in this area of the world is also a well known problem.

[sabenaboy]

Huh? Am I missing something? Are there companies that leave the wx-radar on all the time? What is that good for?
I have been flying 12 years for 3 different companies and I never heard of a SOP to leave it on all the time!

We don't ever turn or leave the wx-radar on when it's obvious that it's not needed.

Regards,
Sabenaboy

[Gooneyone]

Quick question folks. Are we talking about turning it OFF or leaving it on Standby? Some difference here.
First sector, turn it on, all OK, then on STBY until needed.

[Short_Circuit]

From a maintenance point of view, modern WXR has a pencil beam radiation produced by the slotted design of the antenna plate.
It only radiates away from the A/C in a 180 deg arc. The power levels today are in the order of 75 watts compared with the
hundreds / thousands of watts of the older units with many side lobe beams.

Predictive Windshear Operation included in new units operates below about FL200 and would be desirable
to have this function working at altitudes below this.

I have not seen proof of antenna icing up and not scanning, but if it did it would be due to low motor torque due to wear & tear
not to mention very poor seals in the radome.
If your SOP’s allow for turning off (stby) it will extend the life of the servomotors particularly during Your current flight.

P.S. Most A/C the OFF or STBY the T/R's are powered up but transmit is inhibited & antenna stationary

[robin747]

Guess 'Wiggy' and 'Short Circuit' have reasons. I recall during and preceding the 1st Gulf War in the '90's it was standard procedure to keep the Radar 'on' to improve the radar signature.
It makes sense in the current climate too. Unless you are doing a polar route at FL 350+, then you and the Radar can chill! :cool:

[Wingswinger]

It is not to do with improving radar signature, it's because leaving the WXR on allows military units to look at it's frequency band, PRF and scan patterns and therefore identify your aircraft as an airliner.

[Capt Claret]

Flew the BAe146 for several years, Wx Radar only turned on when needed, or in the dark, when unsure if it was needed. Lots of Wx radar problems.

For the last 2 years I've been flying the Douglas B717 :} where the radar is turned on entering the runway for take off and stays on until the after landing scans. I've yet to have an unserviceable radar in the 717.

[ChristiaanJ]

SmokeAnd Noise,
EGPWS does radiate, it uses the radio altimeters.
Re the safety: the 50W to 100W quoted goes into the pencil beam in the front of the aerial. All you get behind the aerial is a few milliwatt spillover.
And if you're inside the aircraft, all of that gets reflected by the aircraft structure, so it doesn't even get to you.
Bears absolutely no relation to the 1W to 2W that your cellphone pumps out right next to your ear and brain.
Re switching it on and off:
My experience with all kinds of electronic equipment is that most failures are caused by the transients when switching it on and off, not by keeping it running.
The only reason I can see for switching it off might be to reduce wear and tear on the mechanical bits (antenna pedestal), and in old models that still use tubes to prolong the tube life (although they don't like switching off and on either).

[FlyingTom]

I like to leave it on as a TCAS back-up in clear skies. There are planes up there with TCAS turned off due to defects. I first noticed how useful it was when we had a no TCAS one day.

[stilton]

Took off a few years ago in the 757 on a dark night heading out over the water and flew straight into a rather bumpy CB.

Had not seen any lightning prior to departure, (hadn't seen anything for that matter)

After turning on the Radar we could see cells everywhere and dodged the rest.

I turn it on and leave it on for the entire flight now, regardless of conditions, day or night, you never know when there might be something out there that you would have thought unlikely.

[ChristiaanJ]

stilton,
I thought that was the mentality of every professional pilot on here in the first place, so I was rather astonished to even find a topic about turning off WX radar in flight.

[ShyTorque]

I leave mine (helicopter wx radar) at STBY after start checks and also if not using it in flight, rather than OFF. When switched off, the antenna can vibrate against the end of the gimbals, which can't do it any good. At STBY it perks up off the stops.

[ChristiaanJ]

ShyTorque,
Dead right about the reason or not leaving it at OFF.
But what about the argument for the STBY?
Just pedestal wear, or something else?

[SmokeAndNoise]

ChristiaanJ

...now I don't claim to be an engineer so correct me if I'm wrong. To my understanding the EGPWS uses an internal database of terrain in combination with a GPS position and therefore does not radiate. Basic GPWS (that modern aircraft still have in addition to the EGPWS), like you say, uses the radio altimeters. The difference is that we're sitting closer to the radar than the rad alt antenna - depending of aircraft type of course.
If you say that there's no radiation on the backside of the antenna and that the nose cone doesn't reflect any radiation back in our direction I suppose I'll just have to take your word - even if it sounds quite unlikely to me.

SAN

[DooblerChina]

75/76

You can only have terrain or weather displayed, CAVOK, mountainous area, I know which Id choose. :ugh:

[ChristiaanJ]

SAN,
You're right about the EGPWS.
If you say that there's no radiation on the backside of the antenna and that the nose cone doesn't reflect any radiation back in our direction I suppose I'll just have to take your word - even if it sounds quite unlikely to me.

Right again.
It's not somebody with an alleged radar background on an internet forum, like myself, who can convince you the 'backscatter' from the wx radar into the cockpit is negligeable.

Why not drop in on your radio/radar workshop, which almost certainly will have a field strength meter sitting on a shelf, and ask them to bring it along next time they have to do a check on the wx radar, do some measurements in the cockpit, and explain them to you?

And if they have a suitable wide-band field strength meter, they can even compare it with your cell phone.

Far better that way to explain and comprehend the issues, rather than taking my word for it.

[ChristiaanJ]

DooblerChina,You can only have terrain or weather displayed, CAVOK, mountainous area, I know which Id choose.Can somebody here elucidate an ancient?
Do the latest weather radars still have a MAP mode?
Older wx radars had a spoiler plate or similar arrangement to create a rough approximation to a cosine² beam in mapping mode, but recent ones seem to use a pencil beam even for mapping, and just let you play with the tilt.
True or false?

[FlyingTom]

Think about it, if there's backscatter your tea won't get cold. :O

[ChristiaanJ]

Think about it, if there's backscatter your tea won't get cold.I woudn't know... never touch the stuff.

[stilton]

Not really true you can only have wx or terrain displayed on the 75/6.

One Pilot can select terrain on their side with wx on the other.

Standard practice with us.

[A-3TWENTY]

Day light...If necessary;

Night...ALWAYS...

[Spotlight]

Chritian J

Pencil beam only as far as I understand your question.

For others:

Some modern displays overlay wx on map, others as has been mentioned can have wx one side of the panel, map on t'other, or even wx and map side by side on the same screen.
The best (to my mind), EGWPS map and 'Target' flashing if any unfriendlies detected.
The previous poster pointing out condensation causing gimble and other probs is correct. Some types suffer badly from Radar location. Not such a problem with newer units that do not utilise moving antenna, but why on earth would you want to take heat away from electronics when operating at -56C.
Even on pre-landing, STBY is prefered to OFF.

[stator vane]

our type on the 738 only has "test, WX, WX/TURB/MAP positions on the unit box--

"TEST-
tests weather radar system operation-
allows test pattern and any fault messages on navigation display MAP, center MAP,VOR and APP modes, with WXR selected.

Note: if the airplane is on the ground and the thrust levers are not advanced for takeoff, WXR tests the predictive windshear system (PWS) indications...deactivating WXR on the EFIS control panel will NOT discontinue the test and can result in automatic WXR activation on both pilot displays. test last approximately 15 seconds."

only other switch is the EFIS Control Panel-WXR-"energizes weather radar 'transmitter' and displays weather radar returns--limited to 320 nm"

sounds as if some parts of the unit remain powered regardless of the various switch positions-and only the display or 'transmitter' itself is controlled by switches.

[ChristiaanJ]

stator vane,...only other switch is the EFIS Control Panel-WXR-"energizes weather radar 'transmitter' and displays weather radar returns--limited to 320 nm"Deactivating WXR on the EFIS control panel is the equivalent of the STBY position of the selector switch on older models. The transmitter is switched off, so the system no longer radiates.
The rest remains powered up.

[Mephistopheles]

I believe the A330/A340 FCOM says turn it on when entering the r/w then off when leaving the r/w after landing. So I guess there is no discussion there at least. Also it is a requirement to have it on when flying in the Arabian Gulf region. Never heard of a wx radar failing coz it was left on too long!

[Dan Winterland]

The 320 is the only aircraft where I have seen the SOPs have the radar 'as required'. Persoanlly, I don't like it - for the reasons discussed. I have seen people fly towards large clouds with the comment "There's nothing in there", to which my answer is usually "How do you know? The radar's off!".

I can see the maintenance arguement. But on the other hand, I've heard that switching it off in flight with the avionics cooling in full flow can cool the magnetron too quickly which shortens it's life.

And leaving it on in areas with 'military tension' is a very good idea. The military aircraft I used to fly had a Radar Warning Receiver which would identify a radar as a civilian weather radar. It might just just prevent you getting a rocket up your @rse!

[eight16kreug]

Flying in the Asia Pacific region, WX radar is ALWAYS required, even off the monsoon season. Bad enough there exists something called CAT, why diminish pilot info by switching the thing to off or stby?

Or do you also switch off the nav and taxi/turnoff lites during daytime to save your airline some bulbs?:confused::confused:

[CJ Driver]

Or do you also switch off the nav and taxi/turnoff lites during daytime to save your airline some bulbs?
Er, yes of course. The bulbs are not expensive, but your very expensive jet will be grounded if they burn out and then you want to fly in the dark... :hmm: