Wx Radar Squat Switch??

skycowboy

skycowboy

New Member
Does anyone familiar with the Citation X know if the weather radar operates off a squat switch? Is there much chance of getting beamed on the ground if the radar isn't in test mode?
 
Never heard of ANY aircraft that have that feature. It would be a very bad idea in terms of flight safety with virtual no real gain to people on the ground with the power of the modern units.
 
On the ERJ the weather radar does not work when you're on the ground....The air/ground logic is involved. We can however turn it on prior to TO for instance..But I'd have to kill you if I told you how we do it!
 
Lemme guess - hit the "STAB" four times in 3 seconds?

Seagull - serious question, why is that some say 2 feet infront of the Radome is safe, where as others say 15 - 20 ft? Companies playing CYOA (cover your own...)?
 
skycowboy said:
Lemme guess - hit the "STAB" four times in 3 seconds?

Seagull - serious question, why is that some say 2 feet infront of the Radome is safe, where as others say 15 - 20 ft? Companies playing CYOA (cover your own...)?
Click to expand...

It's all based on the issues surrounding the very early units, which put out around 3000 watts or more. Current units, at less than 150 watts, would be hard pressed to cook a hummingbird egg.
 
Ok the Citation X has a Primus 870 color radar with a 10 Kiliwatt (10,000 watts) transmitter? soooooooooooooo?
 
Just don't try to have kids in the next 6 months.....

Hey...sounds like the Citation X has a similar radar as the ERJ...Not sure exactly which unit we have but it's a primus 10kW, so...I'd say it possible they have the weight on wheel logic.
 
well hell I don't know if the radar was on or not - the apu was running though... but i was messing around out infront of the radome on a citation X (within 12 feet)... i was basically running a what-if scenerio... and yes they do have the the weight on wheels logic... more curious if they were testing at the time what it would do (one of the pilots was messing around with the panel at the time).

plus the fact that I am a biology major, that is health oriented. Ignorance is bliss and when it comes to health stuff - i don't have that luxury...
 
skycowboy said:
Ok the Citation X has a Primus 870 color radar with a 10 Kiliwatt (10,000 watts) transmitter? soooooooooooooo?
Click to expand...

That sounds like a lot of power for a modern unit, in fact, too much power to make any logical sense. I find it a bit hard to believe. So, they use 150 watt units in 747, 777s, MD11s, etc, but put in enough power to blow up fuel barrels in a little airplane? Either you read it wrong, or their own documentation is wrong.
 
I would wonder if that is actually the transmitting power or the power going through the system itself.

The other factor is dish size, the smaller the dish, the less ability the set has. Can't fit a 30" dish in a small airplane.
 
Ok so the Primus 400 has a 10 kilowatt receiver/transmitter/antenna RTA according to a site... It packs the same wattage as the 880...

Another site says:

10kW nominal R/T power output
Power Output: Nominal 10kW peak

In Engineering doesn't "Nominal" represent "normal"??? So is this thing really spewing out 10KW of power?
​
 
The CRJ radar (Collins WXR-842) has no WOW switches. It has (ours anyways) has two independent controls so both pilots can have their own set up. I know in the Dork, both pilots had to have their radar turned on for it to work on the ground. There is no such requirement on the CRJ. The system used 35W nominal and is rated safe anywhere outside 3 feet from the dish. A Bombardier rep told me that there is actually no min safe distance but for certification purposes they had to list something and 3 feet is about the distance from the dish to the tip of the nose cone.

The difference between radar now and in the past is that most airplanes now have Solid State digital radar which uses a whole lot less energy then older sets.
 
FWIW, the radar in the Caravan I fly goes to standby automatically sometime just after landing and I think it is a function of groundspeed from the GPS. The GPS and radar feed into a common MFD though.
 
Howdy....I'm back

Honeywell is, in fact, a 10,000 watt radar (as opposed to the 60,000 watt radars we had when I got hired by the airlines).
If you have a squat switch to keep radar off, it can be bypassed by maintenance AND SHOULD BE.
The minimum safe distance from a Honeywell radar is 12.5 feet, but I always suggest 50'. The 12.5' is based upon a healthy human, and does not take into account 'pace makers'.
Four things 'hurt' someone on the ground:
1. Antenna size...the focus of the energy
2. Wave length... how deeply you penetrate
3. Power.... that's heat to 'cook em'
4. Time...how long do you Bar-B-Que?
The Rockwell Collins radar has 24 watts, as does the Honeywell RDR-4. You can stand with your belly to the radome all day long. There's not enough power to injure you.

I'll be happy to amplify, but you need 15 degrees up for takeoof with convective weather in the immediate vicinity, and when within 15 NM of the airport (& convective activity) 15-degrees up for approach and landing.

At FL250 you're well above the freezing level, and ice is a very poor dielectrical component to return energy. From 18 to 25 it sure isn't low level rain showers, and you have (1) verified convection (2) have seen the effects of the 500mb winds, the most influencial, and (3) measured the strength of the updraft to hold that much moisture aloft for your inspectiion.

Any questions? I'll be on the Forum more often and do 'better'.
Dave Gwinn
www.davegwinn.com
 
Gee. How did I miss this thread?

Yes, the Radar in the Citation X does have a squat switch to inhibit radar on the ground. And yes, you can disable that feature with the "STAB" button. The only annunciation that tells you the status is the FSTBY (Forced Standby) message on the MFD. If it says "WX" it's on.

I can't imagine a reason a crew would be "testing it" on the ramp, they were probably just getting a clearance. If you looked in the cockpit and saw lots of pretty colors on the MFD, it was probably the EPGWS map.
 
Dave

Very interesting. I wasn't aware that anyone was using those high powers anymore. Why would they use so much power when it's obviously possible to have plenty of capability with such low wattage?
 
Yeah there was no Wx in the immediate area so doubtful it was on.... But why the heck do they use such a huge radar?
 
You must log in or register to reply here.
Back
Top