Driving off birds using acft radar
 

Hi Guys, in one of my recent line verification, the TRE told me something I had never heard before (I have been flying for 35 years now !) ...
The statement was: " ... you can use your airborne radar to drive off birds in the vicinity of the airport ... claiming that the birds "feel" the waves and run away ! ".
For me it does not make any sense. I do not know any animal in the earth (including us) that would be able to "feel" electromagnetic (radio) waves. In the other hand, if this statement has a minimum chance to be true it would be written in the radar's manual, I think !.
Thinking a little bit more, at airports we have ATC radars (mainly primary ones), ground radars and meteorological radars and if this would be true the birds would not be a problem at all !
Does anybody heard this before ? Any suggestion is appreciated !

Do the maths. The ERP from the on board radar is miniscule. Its voodoo.

I recall seeing this written in the airfield info for Faro. It requested pilots to switch on weather radar for arrival and departure as a trial in scaring off birds.

Sorry but that is a myth; trials were run some years ago and as you say birds can't sense radar waves any more than we can.

Birds will react to forward facing white lights, though. The RAF encouraged us to use our landing light/ searchlights when operating at low level.

Douglas/Boeing 717 - radar on entering the runway.; radar off leaving the runway.

The only places I haven't suffered a bird strike are on the apron or a taxiway, where the radar is Off. :hmm:

I first read about that circa 1978 and after that diligently scanned the runway ahead (737-200) prior to departure from Pacific atolls where sea birds concerned us. Had only one bird strike over several years but I always thought it was a dodgy theory. But like believing in God, thought I would cover my arse, "just in case."

Then I happened to read the Collins WXR-700X Pilots guide, (October 1974 edition) and at page 33 it states:

"The average radiated power density of the Collins WXR-700X Weather Radar System is significantly less than the 10mW/cm2 allowable for limiting the exposure of rf energy to humans as noted in FAA Advisory circular, number 20-68B, dated august 1980. The WXR-700X doe not require the use of a dummy load when operated on the ground."

That was in 1974. Presumably the modern radars are safer still?

I have heard this crap trotted out by very experienced and educated Captains and Instructors alike - I always challenge them to explain how this works. As you might imagine, I have never received a wholly convincing answer.
Even if birds could somehow feel the radar, how would they know where it's coming from and thus get out of the way? Most birds don't seem that clever.

You take off with the radar anyway. Will not hurt either, or attract the birds.

I aint when the sky is blue:E

Yes, I am not convinced either, but as Latetonite says "it can't hurt, and even if the birds couldn't care less, it might help someone avoid the CB cloud a little further on. David Attenborough regales us with tales of new scientific and ornithological discoveries that are made every year, as to the previously unknown sensory capabilities of these creatures, so who knows? I am happy to wear odd socks if it is perceived to improve the odds.

De Facto: you don't have to.
But I aint forget to switch it on when it gets dark either, or when I enter clouds, plus it gives me predictive windshear on my plane, a bit earlier than on yours.

Predictive windshear is separate..you dint need to switch the "WX" on to get it,it activates automatically when the thrust levers are set during take off.

Doesn't work. Trust me.

De facto: Right. But with a 12 sec delay. This is for the pilots who forgot the radar..
An airline pilot turns his radar on on TO.

Interesting one. Now, normally I would agree and say that it's an urban myth but a long time ago in a galaxy far, far away, I worked on ground and airborne radars, civil and military.

One of the guys I was working with claimed he could actually 'hear' radar; well the prf from the transmitter, anyway. We did a few experiments and yes, when close enough, he could detect whether the radar was on or not. He had a theory that there was some sort of rectification going on in his middle ear that was stimulating the nerve endings, giving him the impression of hearing a quiet "chirp". Whatever the true explanation, he did seem fairly unique among us.

So, there *may* be a grain of truth there somewhere. One for Mythbusters?

I once knew about a guy that had a pet turtle, he claimed that on occasion that turtle told him to call in sick and that something always happened on those flights.:}

Actually Saxonbloke, I have also seen that on an approach chart somewhere recently, and it wasn't Treviso.

Maybe the turtle knows how to avoid birds ... http://images.ibsrv.net/ibsrv/res/sr...lies/smile.gif

Personally, I think its bunk. Never noticed any difference Stby or On.

Primary radar doesn't have any effect on birds, but SSR makes them squawk. :*

Took a bird strike right on the radome once. Caved it in!
The radar was on at the time. Myth Busted!

Nominal power output on one of the radars on A320 is 125 Watts... over a 30" antenna flat plate, that is about 239 cm2. That is 8 times less powerfull than a home microwave, and 16 times less powerfull than a vaccum cleaner.

I bet I can scare the birds off with the vacuum cleaner on full power with better efficiency than the radar! :}

Now, if we strech the theory reaaaaaally good: many migrating birds have magnetite crystals in parts of their beak or brain, which supposedly helps them navigate. Having an electromagnetic wave pointed directly at them could have a disturbing effect, maybe? But even if that ws the case, would it really make the birds fly away? And in which direction? Maybe they'd come flying straigh towards the source! :E

Old friend of mine was a Typhoon fighter pilot during WW2. He said that when German radar controlled anti-aircraft guns were on to him, the first warning was a clicking or similar noise in his headphones (VHF).

He was leading a formation attacking German forces on D-Day. He heard the noise and immediately changed heading. But for some reason one of the formation pilots in his line astern continued straight ahead and was immediately shot down by remarkably accurate AA fire.

However, in the case of birds and radar the theory was the birds were subject to heat from the weather radar - not "noise."

Weather radar energy isn't particularly hot. I know a bloke who was leaning against the radome of a jet, chatting to an engineer, after a while his arm got a bit of a tingling feeling. On return to the cockpit he discovered the radar was transmitting! So leaning against the actual radome with it transmitting he got a slight tingling sensation after some time. Any birds far enough away to have not already noticed the big noisy chunk of metal coming their way aren't going to feel a thing from the radar.

Correct me if I am wrong (story of my life) but I believe the genesis of transponder codes was during WW2 when they were known as Identification Friend or Foe (IFF for short). In the hope that Germans listening in to RAF frequencies could be fooled, various code names were invented. Thus the code name for IFF was "Parrot." And the code name for transmit was "Squawk."

When RAF controllers wished to tell pilots to switch to a new frequency they would say "Squawk Channel Able

If they told the pilot to switch off his transponder the code word was "Strangle" Thus "Strangle your Parrot"

Well, at least that's interesting:)

I remember that until a while ago LIPZ/VCE charts contained the standing order to keep the weather radar on for takeoff and landing in order to scare the birds away. It has quietly been stricken out of the book though; one assumes that this is due to this methods proven ineffectiveness.

Far better to use a couple of blasts of the ground call siren as you start rolling

Latetonite,please be so kind and give me the reference of this 12secs delay.
I dont switch it on when the sky is clear and i am an airline pilot.:p

de facto


I suspect latetonight might me alluding to the fact that on some aircraft the Wx radar does indeed fire up, whether you've selected it on or not, at some point v. early in the take-off roll ( on the 777 the radar begins scanning once the thrust levers go into the take-off range)...you don't get weather returns displayed on the ND's if you've left the switch off, but nevertheless the radar is scanning and radiating to provide Predictive Windshear....and on the triple PWS alerts become active 12 seconds after the scanning begins.

That said I don't believe for one moment that the birds dive for cover because of the radar...

I'll help Latetonite out :E

Thanks Cosmo Kramer.
I usually do not have the memory to know things and quote a valid reference at the same time. But in this case I can refer to Brady's "The B737 Technical Guide".
I trust anybody discussing technical matters about the B737 series has this one in his library.

Sorry by reference i meant the SOURCE.,,where did you get this text from?
You are mentioning the weather radar not the pWS.

From the AMM:

And from the AMM again:
I dont.:E

Yes, PWS comes on above TLA 53 degrees, same microswitch as your TO Warning, but needs warm up. There is also alternate scanning involved, between use of the radar disc for weather and PWS, and alternate scanning for the Captain and F/O, leading to a possible delay of PWS detection of 12 seconds.

Given a 36 sec average time to rotation, the first third of your take off, when the PWS caution is active, you have thus possibly no indication.

I was kind a weary you do not have those reference books handy.

Nowadays most people I train, get their knowledge from SOP's and answering multiple choice questions. Times have indeed changed.

That does not mean I changed accordingly. I like to keep it simple, and have my WX radar switched on at Line up.
In our company we do not pay for the unavoidable extra fuel burn this habit creates.

De facto,
The source is your FCOM Chapter 15 Warning Systems.

And to add to what latetonite already said:

Hence, without turning the WX radar on, you have no predictive windshear alerts for the first 12 seconds, and no predictive windshear alerts after 100 knots.
Basically you are taking off without predictive windshear at all with the radar turned off.

I can tellya that the high-power military radars in our fighters( not the weather radar that the heavies have) would fry a bird or human if turned on when the "target" was a few feet away. We also had interference problems with other systems at takeoff, so the 'dar didn't come on until we were rolling or actually WOW.

BTW, there's a new anit-personnel microwave system out there that will cause your skin to itch and maybe boil out at a thousand meters or so. One of the "non-lethal" systems we Yanks seem to be concerned with, heh heh.

Newer systems like the agile scanned phased array dars on the F-22 and F-35 don't have this problem. Yeah, the B-2 and later fighters.

The FAA has an Advisory Circular regarding distance to stay away from a radar disk. It is the greater distance of 1.) where the radar beam forms away from the antenna and 2.) Where the radiation level reaches 10 mW per square cm.
Honeywell publishes a safe distance of 14 ft away from the center of the disc for their state of the art RDR-4000 series radar, to comply with this circular AC20-68B.
Even in test mode a distance of 3.5 ft is required.

Latonlite,

With no WR selected on there is no time delay....On take off once either throttle goes above 53 degrees the PWS detection is ON. I think you may be confused with the 12 second thing. If WR is not selected on before takeoff then all sweeps of the dish are detecting WS. If WR is selected on before takeoff see below:

Takeoff WR selected on with throttles >53 degrees:

Sweep 1 left to right: Capt WR for the first 3 second period.
Sweep 2 right to left: Both PWS for the next 3 second period.
Sweep 3 left to right: F/O WR for the next 3 second period.
Sweep 4 right to left: Both PWS for the next 3 second period.

And then so on. The most time delay you could have is 3 seconds.

As for the birds..................

Gas Bags,

Please read the quote from Cosmo Cramer from the FCOM.

Then, Chris Brady mentions 12 sec delay, and blames it to warm up time in his publication.

At the end, if I switch the Wx radar on on line up, I am sure it is available when I push TOGA.

Thereby confirming my fears, expressed elsewhere in these fora, about the total and utter tosh being dispensed by those with the title of "trainer"!

Having spent many happy hours on RAF airfields, observing the feathered species cavorting, feeding and possibly breeding within very short distances of those airfields' surveillance and PAR (nodder & wagger) scanners, I would say that the myth seems to live on and we can't get rid of it.

Better to spend your pre-departure taxi phase performing what the engineers describe as a "confidence check", being wary of the quoted 15m radhaz area for humans and the 300 ft hazard area for the aircraft's radar self-damage potential when bounced off other aircraft, bowsers and other vehicles, terminal and other building structures which will reflect damaging signal strength back into the very sensitive receiver circuitry, which is the secret of the performance of modern Wx radars.

Strangely no company even mentions such a check in their SOPs, though the NG MM states that the ordinary weather test, though it fills the screen with pretty colours and blasts off 1 squirt of emf, is not a proper test of the radar's ability to work properly.

Post radar problem rectification, the engineers have to move the 'frame to a suitable position where it can be "fired up" properly to confirm succsessful fixing.

Better to find out before V1 and later, that the "weapon" is not functioning, than to discover the hard way, as some recent hail damage incidents have illustrated?

Maybe a polite request to the relevant "trainer" as to where it is written will provide us all with the Holy Grail of Bird Repellant Radar, meantime remember the turtle story!!

"I dont switch it on when the sky is clear and i am an airline pilot" ????? Highly inadvisable, the sky may be clear on departure, but what about enroute and destination?.

As for that posting referring to a "professional" pilot who believed the weather radar ATTRACTED lightning strikes, now I know there are fairies at the bottom of my garden! :ugh: