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Re: Judging distances in the air

PostPosted:Fri Jun 11, 2021 2:22 pm
by gaznav
kanga wrote:ISTR ex-FJ AEF Chipmunk pilots seemed often to call Final when starting a continuous curved descent from the end of downwind :roll: Perhaps this was legacy of curved pfl pattern via Key procedures.


Oval circuits are still in use for all military aircraft in the VFR pattern. CAP413 still lists it too.
Image

It was the subject of an AOPA study through the University of North Dakota, listed here by Flyer: https://www.flyer.co.uk/rectangle-or-ov ... is-better/

It was supposed to offer a better solution to loss of control, but I never saw the study conclusion. Anyone got a link?

Re: Judging distances in the air

PostPosted:Fri Jun 11, 2021 10:50 pm
by riverrock
The results of the study were pretty positive but I don't remember much reporting of it at the time?

https://www.google.com/url?sa=t&source= ... U_Uxe5kVdw

Using flight data monitoring equipment, a comparative statistical analysis was conducted
between the rectangular method and rounded base method to evaluate variables that influence AOA and determine if the rounded-base method provides an increased level of safety. Results suggest that the rounded base method does allow for lower bank angles, lower pitch attitudes, lower vertical speeds, and more consistent indicated airspeeds throughout the maneuver.
Additionally, the rounded-base method considerably reduces the likelihood of runway overshoot during the turn to final.

Re: Judging distances in the air

PostPosted:Sat Jun 12, 2021 10:29 am
by gaznav
@riverrock thanks. I’ve not read that before. It’s a good start, but looks like it needs another study to look at experience levels. I’ve only skim read it, but it doesn’t seem to mention the “tightening wind” phenomena either, where a wind from the downwind side of the circuit makes the individual start to increase AOB (and in return AOA) as they start to notice that they are going to blow through the centreline. In a past life I’ve had to ask students to go around as the normal 10AOA has slowly increased to 19AOA due to this. So again, that would need to be taken into account.

But the final line is definitely indicative of oval circuits being something to try to reduce inflight loss of control (I-LOC or LOC-I), which remains our biggest killer.

The general aviation community should embrace the opportunity to reduce I-LOC occurrences by considering the use of the rounded-base method to fly a traffic pattern. I-LOC will continue to present itself as an issue until more creative mitigation strategies such as the rounded-base method are developed and introduced to the aviation community.

Re: Judging distances in the air

PostPosted:Sat Jun 12, 2021 5:30 pm
by Kemble Pitts
lobstaboy wrote:OK, so how exactly do we define "overhead"?


If you fell out of the aeroplane, would you hit it?

Re: Judging distances in the air

PostPosted:Sun Jun 13, 2021 7:00 am
by NDB_hold
Hit what, though? Hit the ARP or just land within the airfield boundary?

Re: Judging distances in the air

PostPosted:Sun Jun 13, 2021 7:31 am
by lobstaboy
Kemble Pitts wrote:
lobstaboy wrote:OK, so how exactly do we define "overhead"?


If you fell out of the aeroplane, would you hit it?


You'd have to allow for ground speed and windage - like bombing from altitude. I suppose we could mandate carrying a Norden bombsight in the aeroplane but even then accuracy would be pretty poor.