Myth Buster Pilots

[Jmmccutc]

Myth or thruth? i was told a while ago that if on a larger jet (ie. Gulfstreams, Lears, CRJ, ERJ, 737 ect.) that if you turn on the storm scope while parked and some one walks infront of it you can cook them with microwaves, or cook eggs on the raydome... i know this sounds like i've been smoking crack, but i swear i haven't, can any of you guys answer this and let me know if there are any sort of SOPs out there that say you shouldn't turn the thing on when parked at a gate or on a ramp...

i think this would make a cool myth busters show...

 

[JJJ]

I think on the CRJ the "danger area' is either 2 or 3 feet from the radome.

 

[ShawnC]

Microwaves were developed by a scientist that noticed that his candy bar in his pocket, melted when he walked through the radar testing room.

So it can be dangerous.

 

[FL000]

Answer to Question #315 Submitted to "Ask the Experts"
Category: Microwaves, Radar, and Radiofrequency

The following question was answered by an expert in the appropriate field:

Q: What are the known health risks to microwave radiation such as that used on commercial aircraft weather radar. Assume everyday exposure 10 ft from radome in an occupational setting.

A: The prime mission of airborne weather radar is the detection, processing and display of weather phenomena with the objective of generating advance warning of potentially threatening weather. A typical state-of-the-art Doppler radar is capable of providing real-time surveillance and advance warning of potentially severe weather systems to pilots, and definitely contribute to the safety and well being of all people who fly. An example of this type of system is the Rockwell Collins WXR-700 color weather radar (military designation FMR-2000-X). This system is widely used in commercial and military aircraft. This system provides full precipitation detection, turbulence detection, forward-looking windshear detection, and an additional skin paint mode capable of detecting tanker size aircraft out to 20 nautical miles. This system uses a coherent Doppler X-Band (9300 – 9500 MHz) transmitter with a nominal output of a few hundred watts of microwave power.

In general, these systems are not operating when the aircraft is on the ground. However, there may be circumstances, especially during maintenance and testing, that ground personnel may be exposed to the X-band radiation emitted by the system. It should be noted that X-band systems are widely used in military aircraft, especially in high powered fire control systems found for example on the F-15 and F-16 aircraft. Therefore, there is much experience on the evaluation of emitters in this frequency band. Commonly available broadband instrumentation used to measure microwaves is extremely accurate in this frequency band, primarily due to the short (~ 3 cm) wavelength of the emitted microwave radiation. There is a large database of calculated and measured hazard distances of X-band systems. The power output of weather radars, however, is many orders of magnitude lower than fire control radars. While fire control systems have the potential to overexpose personnel, it is a common misconception that any system found in the radome of an aircraft nose is dangerous. This is basically incorrect for modern weather radars.

It is quite correct to say that antennas operating in this frequency band produce very narrow, almost pencil-like beams at distances less than 10 feet from the antenna. Typically, these beams will also be scanning. Both these conditions will tend to minimize an individual’s exposure to the microwave radiation. In the X-Band region, the IEEE C95.1 Radiofrequency Radiation Standard(1999), as well as the ACGIH Threshold Limit Value (2000) has an exposure limit of 10 mW/cm2 for controlled (occupational) exposures, averaged over 6 minutes. For uncontrolled (essentially public areas), the IEEE has a exposure limit of 6.67 mW/cm2, with a slightly longer averaging time.

Measurements made on a typical WXR-700 system by the USAF in 1996 were unable to produce levels that are above either the controlled or uncontrolled limits recommended by IEEE. Therefore, in general, it is safe to assume that these systems are de minimis emitters that under normal operations on the ground, are incapable of overexposing personnel to recommended standards in wide use both in the United States and the rest of the world. In the case of Europe, the recommendations of the International Commission on Non-ionizing Radiation Protection(ICNIRP) are often used, and they are very similar to the IEEE/ACGIH limits. Of course, in operating these systems, it is important to follow the manufacturer recommendations, and never to place any part of the body in region of the antenna and the feed horn. This area is always potentially dangerous. However, it is unlikely, when the system is operating normally on the flight line, that levels exceeding IEEE, ACGIH, or ICNIRP will be encountered by ground personnel.

Older systems generally operating at lower frequencies (1000 – 2000 MHz) are becoming less common, but would have similar characteristics.

Reference:

Consultative Letter, AL/OE-CL 1996-015: Report of a Radio Frequency (RF) Radiation Hazard Survey of the C/KC-135 E/R Weather Radar System, WXR-700X, Radiofrequency Radiation Branch, Armstrong Laboratory, Brooks AFB, Texas (1996).

John Leonowich, PhD
Batelle Pacific Northwest National Laboratory

linky dink

 

[avbug]

Bottom line; yes, walking in front of radar is hazardous...and it's not just a few feet. Take it seriously.

A stormscope is not dangerous, as it does not emit radiation. It works in a similiar fashion to an ADF receiver to determine the position of electrical activity (lightening) as an aid to detecting convective activity and storms.

 

[DCitrus9]

Bottom line: it depends on the aircraft. Newer aircraft, such as the 717, are low emitters and are (relatively) safe. Now the DC9, cover your nuts or you'll have some cooked eggs!

 

[flint4xx]

I must have poor reading comprehension, but I thought the Phd from above said it wasn't a threat. (unless you went to an awful lot of trouble)

 

[Timebuilder]

The doc was referring to a modern system.

Older systems used more power, and WWII guys who had high exposure levels often died of leukemia. We've learned to do more with less energy than those days when we had no idea of the effect on humans.

 

[Flying Illini]

I walked 1-2ft in-front of the nose of a Falcon 20 while the radar was still operating...that was several months ago and I feel fine <twitch>.

 

[avbug]

I must have poor reading comprehension, but I thought the Phd from above said it wasn't a threat.

Of course, in operating these systems, it is important to follow the manufacturer recommendations, and never to place any part of the body in region of the antenna and the feed horn. This area is always potentially dangerous.

 

[CrewDawg]

Working around F-16's we deal with with this. I'm not quit sure all the distance's, that's more of a avionics thing, but I know that when certain systems such as the ECM pod are running you need to be a certain distance away, so you don't cook your insides.

 

[FN FAL]

haha...she said storm scope! Sorry, storm scopes don't that sort of thing. But I wouldn't worry too much about them radars frying your insides while you are mashalling planes in and out of the FBO in between students and washing planes...you won't be getting enough exposure.

 

[Jmmccutc]

another question...do those domes get hot to the touch or does the constant flow of air durring flight keep them realitively cool?