Mark and Wombat,
The 50 foot rule predates 1986. I dragged out my old instructors manual
(the light blue folder one) and that shows a diagram with "50 ft over
obstacles" on it in the circuit appraoch and landing section. Also
reference to it in the text, in the first paragraph after the heading
"Base turning point" is the sentence "If there are obstacles we must
ensure that our final approach path clears them by approximately 50ft."
I am pretty sure I had this book by January 1984 (my assistant
instructor course) and may have had it earlier. The diagram looks a bit
scratchy as if it had been copied from an earlier document(s). I would
guess the older green folder instructors manual (from the 70s) had the
same illustration, and probably wording.
Regards
SWK
On 17/10/2012 6:32 PM, Mike Cleaver wrote:
HI Mark
I may be able to help re the 50 ft thing. Back in 1986, at the
pre-Worlds prior to the Benalla 1987 Worlds, a French competitor hit a
power line 4 km from the airfield flying at or over Vne, removed the
tailplane from his glider, and was killed. Between us, the GFA (Mike
Valentine RIP) and CASA (myself) devised some changes to the rules for
low approaches exemption from the CAR requiring 500 ft above obstacles
except in the course of landing, to say that a glider within 5km of
the finish of a race could descend below 500 ft if the flight was in a
contest approved by the GFA, with the proviso that the glider was kept
in sight of the finish line, not less than 50 ft clear of obstacles,
and with sufficient energy to either make a safe circuit or to land
ahead on the airfield.
That rule has subsequently been changed at least twice, but may be the
source of the 50' figure you quote. The current rule applies to any
flight away from the aerodrome and allows a low finish "in accordance
with the GFA Ops Regs" and there has been a GFA endorsement for flying
a circuit off a low high-energy approach, though nowadays we prefer
straight-in approaches to a long landing (leaving room behind for
following traffic) and with enough energy for safe obstacle clearance.
I was always taught to plan to clear obstacles by around one and a
half wingspans, assuming there was no overriding priority to avoid
hitting the far fence, and whilst always remembering that it was
better to roll slowly into the far end of the field than to fly
through the obstacles at the approach end. It is also far easier to
touch down close to the near fence by using a steep approach with
adequate clearance than a shallow one with little in reserve.
Wombat
On 15/10/2012 1:17 PM, Mark Newton wrote:
Hi folks.
My google-fu is failing me, but at least one of you can probably
help.
I've long accepted that the rule for obstacle clearance is 50'.
However, the GFA instructor handbook describes it as a wingspan,
and the B certificate oral exam calls 50' a "recommended" minimum,
so I'm trying to go back to sources to find the origin of the rule.
And I can't seem to find it written down anywhere.
I'm beginning to suspect that my long-term acceptance of the 50'
rule is wrong, and that the real limit is, shall we say, more
"operationally fluid" than that.
Wondering if the strict mention of 50' that I've seen at clubs all
over Australia is actually more of a tradition, perhaps derived from
a misunderstanding of certified light aircraft performance charts
which give minimum takeoff distances including clearance of a 50'
obstacle.
Does anyone have a cite to the regulations?
(while you're at it, providing a cite to a current GFA or non-exempted
CASA regulation which states what GFA annual check entails, whether
it's required to be signed out in a logbook, or whether an instructor
is even required to be present, would help to settle a long-standing
argument :)
- mark
_______________________________________________
Aus-soaring mailing list
Aus-soaring@lists.internode.on.net
To check or change subscription details, visit:
http://lists.internode.on.net/mailman/listinfo/aus-soaring
_______________________________________________
Aus-soaring mailing list
Aus-soaring@lists.internode.on.net
To check or change subscription details, visit:
http://lists.internode.on.net/mailman/listinfo/aus-soaring
_______________________________________________
Aus-soaring mailing list
Aus-soaring@lists.internode.on.net
To check or change subscription details, visit:
http://lists.internode.on.net/mailman/listinfo/aus-soaring
