|It was a typical
August morning in southeastern Connecticut. Pulling
back my window shade around 6 a.m. revealed some
low clouds hovering somewhere above the treetops,
but the promise of the day was that the fog and
low clouds would burn off, giving way to morning
sunshine. Although just a few miles away the morning
sun was already shining, at Groton-New London Airport
(GON), those lingering low clouds would shortly
be the undoing of two pilots then on a final approach.
Around 6:10 that morning, a chartered Learjet
35A departed Republic Airport (FRG) in Farmingdale,
Long Island, on a short positioning flight to
nearby GON. The crew was to pick up two passengers
in Groton and fly them to a business meeting in
Buffalo, N.Y. Weather in the region was basically
VFR, but with localized areas of low clouds and
fog. The automated weather observation at Groton
airport reported 4,100 scattered and 9 miles visibility.
In reality, conditions to the south and west were
clear, and a 10-knot breeze from the southeast
combined with a 2° temperature/dew point spread
churned up the usual low clouds and scud just
to the north and northeast of the airport.
Approaching from the shoreline about 7 miles
west of the airport, the pilots reported they
had the airport in sight and canceled their IFR
flight plan. The aircraft entered a left downwind
for Runway 23 at about 1,800 feet and continued
its descent as it maneuvered for the runway. Reading
the narrative in the preliminary NTSB report,
it would seem the pilots were having difficulty
maneuvering under VFR for a landing on Runway
23. According to the report, the aircraft turned
base about 2.3 miles northeast of the airport.
About 1.5 miles from the runway -- and while south
of the extended centerline -- the aircraft turned
left and then back right again. About one-eighth
of a mile south of the runway threshold, the aircraft
made a 60-degree right turn back toward the runway,
crossed the runway at about 200 feet agl, and
then turned back left toward the center of the
The left turn continued, and the aircraft re-entered
a left downwind at about 300 feet agl -- well
below the 640-feet circling minimums for the airport.
The last radar contact put the aircraft about
one-eighth of a mile from the end of the runway.
A witness preflighting an aircraft at the time
watched as the Learjet entered the downwind but
lost sight of it as it skimmed or passed behind
the low clouds. The aircraft reappeared about
200 feet agl and appeared to overshoot the extended
runway centerline. According to the witness, the
bank angle increased to about 90 degrees, and
as it turned final at low altitude, the aircraft
disappeared behind the trees. It was about 6:39
The crash scene was horrendous. The Learjet clipped
the first housetop, careened through a line of
pines and hardwoods, and slammed into two more
homes before tumbling into the Poquonnock River.
Fuel sprayed through the air, igniting in an intense
fireball. Almost miraculously, nobody on the ground
was killed, but one woman was injured while she
jumped from a bedroom window as her house was
suddenly engulfed in flames. Another family survived
only because they had spent the night away.
The area was closed off as firefighters battled
the flames and later as crash investigators scoured
the scene and sifted through the wreckage. By
the time I arrived from my home, barriers had
been erected to keep the public at bay, but the
charred remains sent shivers up my spine. The
glaring question, of course, is how and why did
two highly experienced professional pilots get
themselves into such a tight corner?
While it is unclear precisely why the pilots
elected to land on Runway 23 when the approach
to Runway 5 -- which has an ILS -- was reportedly
clear of clouds, the fact is that they entered
the downwind and attempted a "standard"
traffic pattern to the usual no-wind runway. Unfortunately,
the pattern was anything but standard.
When reverting to visual flight rules in generally
sunny and clear conditions, it's easy to disregard
the standard procedures that would be followed
when conducting a circling maneuver at the end
of an IFR approach. Although the flight crew in
this case had canceled IFR and was making a VFR
approach to the field, they might have fared better
had they abided by the published circling minimums
and followed standard operating procedures (SOPs)
for a bona fide circling approach.
Circling approach procedures may vary from one
operator to another, but a number of common threads
run through the fabric of various operators' SOPs.
Although not specifically required by regulation,
some operators require that the MDA be maintained
until the aircraft has maneuvered to within a
30-degree angle of the extended runway centerline.
operators require the use of an autopilot
during a circling maneuver, with "altitude
hold" mode selected to maintain the MDA and
"heading select" used for course tracking.
Restrictions or even prohibitions on the use of
circling approaches at night -- a visual condition
that heightens risk -- are also common among many
"According to our SOP," explains one
flight manager for a fractional jet operator,
"we can perform a circling approach only
in daylight, and then the conditions must be at
least 1,000 feet and 3 miles."
Other aspects of the circling approach are more
clearly defined and universally accepted. According
to FAA Order 8400.10, Air Transportation Operations
Inspector's Handbook, which details the content
and performance standards of FAA flight checks,
"The circling MDA must be maintained until
an aircraft [using normal maneuvers] is in a position
from which a normal descent [less than 1,000 fpm]
can be made to touchdown within the touchdown
Even a proper circling approach has its drawbacks.
While a circling maneuver as defined in 8400.10
implies a stabilized approach from the circling
MDA, some view the circling procedure as running
contrary to the stabilized approach philosophy.
Especially when the decision to circle comes late,
pilots may end up playing catch-up as they set
up and perform the circling maneuver, and the
ideal stabilized approach falls apart at the seams.
At the very least, the circling maneuver requires
a departure from a constant rate of descent as
the aircraft levels off to complete the circle.
The Stabilized Approach
The importance of a stabilized approach has long
been recognized in the turbine aircraft world.
By definition, a stabilized approach is one in
which the aircraft is properly configured and
maintains a constant airspeed and descent rate
as it follows a constant vertical flight path
to the touchdown zone.
The underlying philosophy of the stabilized approach
as outlined in FAA Order 8400.10 is that it allows
pilots to "determine displacements from the
course or glidepath centerline, to mentally project
the aircraft's three-dimensional flight path,
and then to apply the control inputs necessary
to achieve and maintain the desired approach path."
More specifically, the stabilized approach technique
allows a pilot to more readily recognize when
problems such as wind shear cause the aircraft
to deviate from the desired flight path or airspeed.
Perhaps just as important is that flying a stabilized
approach keeps the workload to a minimum during
a time when a pilot's attention must be keenly
focused on the world around him.
Most operators, as recommended by the FAA, have
SOPs that require pilots to be stabilized 1,000
feet agl for an instrument approach, or 500 feet
agl for a VFR approach. As described in the Flight
Safety Foundation Approach and Landing Accident
Reduction (ALAR) Risk Awareness Tool Kit, the
recommended elements of a stabilized approach
include a number of criteria, including correct
flight path, airspeed, configuration, descent
rate and completion of all briefings and checklists.
Despite the emphasis placed on stabilized approach
procedures, some operators still don't embody
all the principles in their SOPs. Especially in
the world of light turbine aircraft and small
jets, "stabilized" approach characteristics
can involve slowly reducing airspeed throughout
a lengthy portion of the procedure. As one pilot
notes, "This requires a lot of extra trimming
and attention to airspeed control throughout the
procedure, but it's the way we've all been taught."
The truth is that not all pilots religiously
follow the edict to fly a stabilized approach,
and the results show. According to the Annual
Turbine Aircraft Accident Review 2002 by Robert
E. Breiling Associates, 8 percent of worldwide
jet aircraft accidents in the past five years
occurred during the approach phase. Turboprops
fared worse, with 18 percent of the accidents
occurring in the approach phase. As Breiling notes,
"Unstabilized approach conditions were implicated
in numerous landing accidents, which account for
roughly half of the total accidents."
In an article recently published by the Federation
of Indian Pilots, Capt. Vivek Kulkarni of Air
India states, "A detailed analysis of ALAs
[approach and landing accidents] determined that
CFIT, landing overruns, loss of control, runway
excursion and non-stabilized approaches accounted
for 76 percent of all occurrences. Indeed the
non-stabilized approach was probably the initiating
event in most incidents." In an Obstacle
Clearance Panel working paper presented at a meeting
in St. Petersburg, Russia, in 1996, author J.
W. Gregory makes a connection between unstabilized
approaches and CFIT accidents. It seems likely
that the lack of a stabilized approach contributed
to the sad end of the Learjet 35 crew this past
summer in Groton.
As professional pilots, we like to think we're
well beyond the point at which we could fall victim
to a stall-spin situation, especially in the benign
environment of a circling maneuver in VFR conditions.
But the statistics suggest otherwise. A recent
study by the Air Safety Foundation found that
commercial-licensed pilots are more likely to
fall victim to stall-spin accidents than are private
or student pilots. When a stall-spin develops
at pattern altitude, the chances of recovery or
survival are essentially nil.
Several factors come into play when we leave
the stabilized approach regime and begin maneuvering
around the pattern for a landing. Not only does
initiating a maneuver -- particularly one with
significant angles of bank -- destabilize the
approach, but it introduces further complications.
A critical factor to consider when transitioning
into, say, a circling approach is the relationship
between Vref, bank angle, load factor and stall
speed. For example, a Vref of 1.3 Vso might provide
an adequate margin above stall as long as maneuvering
is limited, but not so when making steep banking
maneuvers required for collision avoidance or
other unexpected situations. Remember that in
a level turn, stall speed increases sharply once
we exceed moderate bank angles.
Up to 20 degrees of bank, the increased load
factor and attendant increase in stall speed in
a level turn are negligible. At 40 degrees of
bank in a level turn, we've increased stall speed
by 14 percent. Increase the bank to about 55 degrees
in that level turn, and we're right at 1.3 Vso.
It's for reasons such as this that some operators
require the use of autopilots for circling maneuvers,
particularly when the autopilots limit the bank
In fact, a circling maneuver provides an excellent
opportunity to make a fatal mistake with respect
to the stall margin. With flaps and gear extended,
lots of additional power is required when leveling
off to maintain airspeed. Distractions outside
the cockpit can easily divert the pilot's attention,
compromising airspeed control and eroding the
margin above stall speed.
I recall clearly the sunny September day when
a Piper Cheyenne returning from a maintenance
test flight at Jefferson County Airport (BJC)
in Colorado got caught in just that trap. While
on a straight-in approach to Runway 11, the pilot
was advised of traffic ahead, and was asked to
slow his speed as much as possible. The pilot
acknowledged, and about 15 seconds later was asked
to make a 360-degree turn to the left for spacing.
The pilot complied.
The aircraft began a steep turn, and was then
seen entering a steep, spiraling, nose-down descent.
The pilot and two mechanics aboard were killed
in the crash. No mechanical failure or malfunctions
were found in the investigation. The NTSB report
concluded the probable cause to be "failure
of the pilot to maintain adequate airspeed while
maneuvering for spacing in the traffic pattern,
which resulted in an inadvertent stall at low
speed." Clearly, the pilot's straight-in
approach had been destabilized, and the maneuvering
load factor played a part in the inadvertent stall.
Further complications come when we attempt to
maneuver with respect to ground references, terrain,
or even clouds. When a pilot attempts to follow
a desired ground track -- such as when turning
to align with the runway -- or maneuver around
terrain or clouds, the focus shifts from cockpit
references to outside references, and airspeed
control can suffer.
Put birds, another airplane or wind gusts into
the picture, and the problem only worsens.
At an airport like Groton, these factors are
likely. Just to the south of Runway 5-23 lies
Bluff Point, a bird sanctuary and recreation area
bordering the Poquonnock River. Rich in shellfish,
the brackish waters of the Poquonnock provide
a haven for a multitude of migratory waterfowl
and numerous birds that reside year-round. Especially
at low tide when the shellfish are more readily
available, flocks of gulls and other sea birds
can be found in the area. The airport is also
home to two flight schools and serves as a base
for an active fleet of light general aviation
aircraft. Hazards in the pattern are not uncommon.
In the case of the Learjet 35 at Groton, it appears
the pilot was maneuvering around low, scuddy clouds,
as well as making a tight turn to final. But yet
another factor may have come into play. Remember
that when maneuvering with reference to the ground,
the highest bank angle occurs when the ground
speed is highest -- i.e., with a tailwind. In
this case, the winds were 150 at 10 knots, meaning
the pilots had a 10-knot tailwind on base, and
thus would have required a slightly steeper bank
angle maneuvering from base to final. This factor
is a minor one at best, but perhaps represents
another nail in the proverbial coffin.
The preliminary NTSB report on the accident contains
one final item of information that's particularly
telling. It says the captain's airspeed bug was
set 20 knots higher than that of the first officer.
It's unclear exactly who was flying at the time,
or where the airspeed bugs should have been set,
but it's clear enough that a 20-knot error in
airspeed combined with even a moderate bank angle
could have put the pilots squarely in the danger
zone. If nothing else, such an error indicates
a breakdown in CRM and suggests that the pilots
may have been rushed.
In fact, "get-there-itis" and time
pressure on the part of pilots and controllers
alike may be the real culprits behind many unstabilized
approaches. As one flight manager points out,
"I've seen this too many times, with pilots
rushing to get somewhere, complying with ATC instructions,
or taking a night visual approach when an instrument
approach would add only a few extra minutes to
In its investigation of the Southwest 737 overrun
accident at Burbank-Glendale-Pasadena Airport
(BUR) in March 2000, the NTSB said a contributing
factor in that career-ending mishap was "the
controller's positioning of the airplane in such
a manner as to leave no safe options for the flight
crew other than a go-around maneuver." Of
course the onus was on the flight crew's "failure
to abort the approach when stabilized-approach
criteria were not met."
The May 2003 Callback, from NASA's Aviation Safety
Reporting System, reports three cases where flight
crews were backed into a corner by ATC, causing
them to violate their stabilized approach mandate.
A circling approach -- or standard traffic pattern
-- is often the maneuver required to complete
a flight, but it's not always as simple as it
appears. Only by developing and strictly following
a clear set of SOPs can we limit the risks that
can turn a simple maneuver to landing into a truly
final approach. B/CA
STABILIZED APPROACH CRITERIA
The following is provided by the Flight Safety
Foundation as part of its Approach and Landing
Accident Reduction (ALAR) Risk Awareness Tools.
More information is available at www.flightsafety.org.
Recommended Elements of a Stabilized Approach
All flights must be stabilized by 1,000 feet
above airport elevation in IMC and by 500 feet
above airport elevation in VMC. An approach is
stabilized when all of the following criteria
(1) The aircraft is on the correct flight path;
(2) Only small changes in heading/pitch are required
to maintain the correct flight path;
(3) The aircraft speed is not more than Vref
+ 20 knots indicated and not less than Vref;
(4) The aircraft is in the landing configuration;
(5) Sink rate is no greater than 1,000 fpm; if
an approach requires a sink rate greater than
1,000 fpm, a special briefing should be conducted;
(6) Power setting is appropriate for the aircraft
configuration and is not below the minimum power
for approach as defined by the aircraft operating
(7) All briefings and checklist have been conducted;
(8) Specific types of approaches are stabilized
if they also fulfill the following: Instrument
landing system (ILS) approaches must be flown
within one dot of the glideslope and localizer;
a Category II or Category III ILS must be flown
within the expanded localizer band; during a circling
approach, wings should be level on final when
the aircraft reaches 300 feet above airport elevation;
(9) Unique approach procedures or abnormal conditions
requiring a deviation from the above elements
of a stabilized approach require a special briefing.
An approach that becomes unstabilized below 1,000
feet above airport elevation in IMC or below 500
feet above the airport in VMC requires an immediate
SAFE APPROACH STRATEGIES
(1) Keep safety a priority, even when schedules
(2) When available, fly an instrument approach
rather than a visual, especially for a night arrival.
Doing so improves instrument proficiency (especially
for non-precision approaches) and heightens safety.
(3) When making a VFR approach, abide by the
IFR circling minimums and procedures.
(4) When possible, choose a straight-in instrument
approach rather than a circling maneuver.
(5) Take steps to avoid situations that destabilize
an approach, and use an approach speed that allows
any anticipated maneuvering.
(6) Consider stabilized approach procedures as
limits, not targets. If an approach becomes unstabilized
below the minimum altitude (1,000 feet agl for
IFR, 500 feet agl for VFR), go around.
(7) Advise ATC and decline clearances if they
violate your stabilized approach requirements.
Reprinted from the November 2003
issue of Business & Commercial Aviation