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[Guest Andys@coffs]

As someone who has worked on Radar in a previous lifeI can say that doppler radar has a couple of design issues that relate to it being doppler. One is that if your in an aircraft travelling at say 500kms/hr then there is a doppler shift related to the 500kms per hr for everything dirrectly in front of you and a reducing cosine related speed for every thing that is left or right of boresight. Clearly the viewer of the radar doesnt want to see all the ground clutter and as such that must be mathematically removed, and is, as a function of aircraft speed, and or ,antenna bearing off centerline.

 

Then there are all the ground objects that dont stay still such as trains busses and cars. they generally only move at speeds less than 150km/hr and as such they also can be removed by mathematical methods. Unfortunately a trike generally doesnt go any faster than a car and as such when removing the additional ground clutter associated with cars etc the slow aircraft are also removed.

 

For Ground attack work doppler isnt as relevant and processed radar returns that arent subject to doppler processing get displayed. The radar (assumptions around equipment age being made by me) will be in one mode or the other, probably not both (although new equip is capable of displaying both and more) and as such you either have few, but relevant air returns, or heaps of gnd returns.

 

I suspect that the sensitivity of the radar, as earlier suggested, as being teh reason for non display is quite inaccurate, and its the fact that in a Airforce conflict scenario you dont need to be concerned with airborne targets doing 100km/hr, however those doing close to or beyond mach, you'll want to know where they are! so as to be able to perform the appropriate "run away" manouveur.

 

For the guy flying the Powered parachute, you have both issues, your radar return, assuming there is one due to very little radar cross section, and the fact that you'll have been OCTA and therefore some distance from the radar head will have been removed in signal procesing due to the realtively small doppler shift that a PPC is able to create.

 

Andy

 

BTW in years gone by the easy way to get around doppler shift was to change you direction so that no doppler shift was created. for eaxmple in a fast bomber flying a semi circle around a known radar head allows you to still cover gnd at a reasonable rate yet not change your distance relative to the radar head until you are far enough away taht is doesnt matter.

 

In the same way a conflict between a fast burner and a crop duster or helicopter etc could easily occur if the early relationship between the 2 didnt generate that much doppler shift, clearly no collision can occur if no doppler shift is created at all, but if it occurs outside of the radars 45degrees of visibility then as they say "Sh*t happens"

 

 

[Guest ozzie]

On reading the above, i am wondering if the RAAF Hawks operating into Singleton restricted area have some form of "seeing" light aircraft.

 

ozzie

 

 

[Guest Andys@coffs]

Indeed, the same Mk1 eyeballs that we have and a reliance on the rules of the road

 

 

[Guest ozzie]

After watching that show on SBS last night, it seems that some of these "trainees" are running right on overload. unfortunatly my doppler is U/S at this time.

 

Near misses. only one, with Scott Winton. Thruster vs Sapphire about 20ft seperation, head to head.

 

actual hits, plenty in the one "incident" but not with any aircraft.

 

whilst in freefall over Proserpine airport as i went thru about 5,000ft i felt what semed to be like rain. (it stings like crazy). i opened at 3000ft and found i was surrounded by thousands of small yellow butterflies.

 

i have had 3 close calls with "weekend warriors" at Picton over a 15 year period.

 

Ozzie

 

 

[Guest browng]

By the sounds of your accident it certainly should be there -

If anybody is interested the report is here; (it's a Word document) http://members.iinet.net.au/~browng/GBPKS.doc

 

And this is the aircraft concerned; Aerobatic,180HP Fuel injected Lycoming, Harzell CSU. Handles much like a 2 seat Pitts.

 

 

 

[Mazda]

I'm aware of two midairs and they have been mentioned here. That Jetranger was flying illegally in a bombing range. Remember the RAF during the cold war had more than 1,000 fast jets and the pilots flew 300+ hours per year. That’s 450,000 hours, mainly at low level, per annum. Let’s say an average of 800kms per hour then that’s two midairs in 36 million flying kms.

 

This is in stark contrast with the RAAF fast jet pilots who have a limited number of aircraft and pilots flying a limited amount of hours per year. Remember too that they train in restricted airspace with no real need to look out for bug smashers.

 

 

[Guest Crezzi]

That Jetranger was flying illegally in a bombing range.

Apparently not - according to the investigation (& my admitedly hazy recollections of the accident and UK airspace)

 

Cheers

 

John

 

 

[Guest Crezzi]

http://members.iinet.net.au/~browng/GBPKS.doc[/url]

Well handled ;)

 

 

[Guest browng]

I'm aware of two midairs and they have been mentioned here. That Jetranger was flying illegally in a bombing range. Remember the RAF during the cold war had more than 1,000 fast jets and the pilots flew 300+ hours per year. That’s 450,000 hours, mainly at low level, per annum. Let’s say an average of 800kms per hour then that’s two midairs in 36 million flying kms.

Indeed, and they also had to share the UK's itty bitty airspace with USAF B52's, F-111's, A-10's, U2's, and other sundry American hardware. In spite of almost being RAF 'roadkill' myself, I think they did a damn fine job, and am frankly surprised that there weren't more 'incidents', given the difficult circumstances they had to operate and train in.

 

 

[Guest Crezzi]

Make that 3 mid-airs - I'd forgotten about this one http://www.aaib.dft.gov.uk/publications/formal_reports/3_2000_za_330_and_g_bpzx.cfm

 

 

[JohnMcK]

Hi All,

 

For interest sake, some years ago while heading to Inglewood (SW of Brisbane) in the Drifter I had a near miss with an F111. I was flying at 500 ft following the road and traffic spotting for my wife who was driving the car below me.

 

She yelled into the UHF "Jet jet" as two F111 traveling at over 500 knots, wings swept back went underneath me. I didn't see them until they were long gone. I spoke to the pilot on the VHF and he said he only saw me because of the bright yellow wing.

 

On my return I went to see the pilots and we discussed the incident. They told me the radar was in ground mode and it wouldn't pick me up. They also told me that because they get so little hours they hand fly at every opportunity. This was very fortunate as the Mk one eyeball of the F111 pilot stopped me going down the air intake. At 500 knots you don't see a Drifter until it is very close. The bright colour was an asset. They went under to stop wake turbulence sending me aerobatic.

 

JohnMck

 

 

[Guest browng]

Make that 3 mid-airs - I'd forgotten about this one http://www.aaib.dft.gov.uk/publications/formal_reports/3_2000_za_330_and_g_bpzx.cfm

That was an interesting read for several reasons;

 

1. The official prediction was one mid-air every six years involving a fast jet at low level.

 

2. It confirms that the only way the pilot who nearly hit me could have seen me was visual.

 

3. Even with a HUD, the Tornado pilot has to do quite a lot of "head down" checks in flight, and when his head is down the back seater can't help because he has almost no forward visibility.

 

The more I read, the more I worry about the trend toward dependence on more and more 'gadgets' for recreational and GA aircraft, when even the best trained pilots in the RAF, with sophisticated equipment, need to ultimately depend on see and avoid, a fact that is clearly stated in this report, and reinforced in John's post above.

 

 

[Guest Crezzi]

Top Story John - thanks for sharing that. You have a commendably quick-witted wife if I may say so.

 

Cheers

 

John