To
Extend Downwind or Not to Extend?
All instructors and all those
responsible for the supervision of flying at all GA airfields are urged to
carefully consider the safety implications of the practice of extending the
downwind leg to fit in with other visual circuit traffic.
Why do
some pilots extend their downwind leg in an airfield visual circuit? Usually
because they have got their spacing wrong and are trying to correct this by
going further downwind to fit onto final behind another aircraft on approach,
or to allow time for a departing aircraft to clear the runway or, perhaps, to
adjust for differing final approach speeds. It seems to me that either
student pilots are being taught to do this as a matter of routine or that it
is a habit they develop after they have completed their basic training. I
suggest that to extend downwind is a bad habit that can lead to difficulties
on the approach, create a sloppy circuit pattern for others and can even lead
to accidents.
Approach With Care
I have
heard Air Traffic give the instruction, “Extend downwind.” I
contend that a pilot flying a visual circuit is fully entitled to respond
with, “Negative. Going around.” He should then follow the
required track and height until he can once again call,
“Downwind” at the correct point in the circuit pattern. Any
competent pilot should be able to adjust his airspeed within the pattern if
this is necessary to achieve safe spacing. Part 2 of the Straight and Level
exercise should have taught him how. Going around again allows him to
maintain correct and safe spacing in the circuit, everyone else in the
circuit knows where everyone is and our pilot can safely fly a standard
circuit down to touchdown. On the other hand a pilot who has extended
downwind by some undefined distance will find himself turning from the
downwind leg onto final at an uncertain range from the threshold. The aspect
of the airfield and of the runway will be unfamiliar. The pilot is now faced
with trying to get back onto a normal approach slope prior to landing. PAPIs
will assist, but many recreational airfields are not equipped with PAPIs or
other approach slope aids. We probably all remember that a 3 degree approach
slope equates to just about 320 feet per nautical mile. A normal power-on
visual circuit in a light aircraft usually involves rolling out onto final
not further from the runway threshold than about one mile and at about 400
feet agl. One of the problems with a long ‘drag-in’ approach is
that it is all too easy to get well below the ideal approach slope without
recognising that a potentially dangerous situation is developing.
Another hazard associated with extended approaches is the fact that
anyone flying a normal, standard circuit pattern may be turning onto final
belly up to you, and descending onto you, as you drag your aircraft in from
miles away towards the threshold. He can’t see you and you probably
will not see him, especially if you are flying a high-wing aircraft. There
have been numerous collisions in this situation.
There have been several accidents to GA aircraft where the common
link in the accident chain has been the fact that the pilot flew an extended
downwind leg prior to striking the ground, or a low level obstruction, on the
approach path.
Gruman GA-7
A Grumman GA-7 light twin was on a visual approach to Runway 22 at
Stapleford Airfield when the fin of the aircraft struck the earth wire
suspended from the top of electricity pylons sited some 1nm from the runway
threshold. The tops of these pylons are 210 feet above airfield level. There
are displaced thresholds on both Runway 22L and Runway 22R with PAPIs set at
4.25 degrees, all designed to provide an approach path with a safety margin
above these pylons. There is a space of 21 feet below the earth wire and the
upper power cable. The Grumman managed to pass through this gap with only the
fin striking the earth wire. The aircraft landed safely.
Why did this pilot hit the cable? The pilot was returning from Le
Touquet to drop a friend at Stapleford before flying on to his base at
Elstree. The weather at Stapleford was CAVOK with a light south-westerly wind
when the pilot joined overhead, descending from 2,200 feet to a circuit
altitude of 1,200 feet on airfield QNH. The time was approaching 1600 hrs on
14 January. Having joined the downwind leg the pilot lowered the landing gear
and the first stage of flap and reduced speed to 100 kt. He was aware of two
other aircraft in the area with one on final and one approaching from the north.
He decided to extend his downwind leg to
give himself adequate separation from these aircraft.
At about 2 nm from the airfield
he turned onto base leg, keeping the other two aircraft in sight. On base leg
he lowered the second stage of flap and descended to 1,000 ft for the turn
onto final approach. He was now Number 3 on the approach. Established on final
track he lowered the third stage of flap and reduced airspeed to 85 kt,
adjusting power to give a normal rate of descent. The runway was visible but
the setting sun impaired his forward vision. As the first aircraft was about
to touch down the second aircraft went around. At the same time there was a
loud bang as the Grumman struck the cable. The handling was not affected,
despite considerable damage to the fin and rudder.
Making no allowance for the sag of the earth cable between the pylons,
the cable that was struck was 210 feet above airfield level at a range of 1
nm from the beginning of Runway 22. Had the pilot been flying a 3 degree
approach slope to the beginning of the runway (not the displaced threshold)
he would have cleared the cable by at least 110 feet. Had he been following
the PAPI slope set at 4.25 degrees he would have cleared the cable by at
least 241 feet. In fact when he struck the cable he was on an approach slope
of less than 2 degrees. Why? Because he allowed himself to be distracted by
the other traffic and flew an extended downwind leg, placing himself well
outside the line of notified power cables. He then flew a
‘normal’ approach path that placed him low enough on the approach
to hit the cable. He and his passenger were lucky to escape unhurt. Others
were not so lucky.
Robin 100
A Robin 100 was returning to Stapleford on 26 December some years before
the above accident happened. The surface wind was 220/15 and Runway 22 was in
use. The circuit was busy and the pilot of the
Robin extended his downwind leg to fit in with traffic. Witnesses on the ground
thought that the aircraft was low on the approach but in a constant descent
attitude. The aircraft struck the power cables. The Robin broke up,
inflicting fatal injuries on all four occupants. Other pilots flying at the
same time commented on the difficulty in seeing Runway 22 in the bright
winter sun. It is possible that the 15 kt headwind exacerbated the
situation.
It is my contention that to extend your downwind leg while flying a
visual circuit is poor airmanship and can lead to an increased workload on
the approach. Any extra distraction can then lead to an unstable approach and
an accident. What constitutes an ‘unstable approach’ and what
should you do about it? Ask your friendly instructor. Extending the downwind
leg may save a few minutes over the option of going around again from the end
of a normal downwind leg but is usually not the safer option.
All instructors and all those responsible for the supervision
of flying at all GA airfields are urged to carefully consider the safety
implications of the practice of extending the downwind leg to fit in with
other visual circuit traffic. All pilots are responsible for their own
safety.
A Final Word – On Orbiting
…
Before I leave the topic of unsafe flying in the
visual circuit I must express my dislike of anyone orbiting anywhere in the
visual pattern. An orbit in the circuit is an ideal way to set up a collision
in the circuit. It really will not reduce the severity of the impact to
present yourself at The Pearly Gates with the excuse that Air Traffic told
you to orbit. You are responsible for the safety of your aircraft and
everyone in it. Orbits in the circuit are unsafe.
The accident details in this article are taken from Air
Accidents Investigation Branch Reports, which source is gratefully
acknowledged. It is not the purpose of AAIB investigations to apportion blame
or liability. Comments and conclusions are those of the author.
Text and Photographs © 2007 Gremline & Hill House
Publications, unless otherwise stated.
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