Feeling
a bit heavy? Got weight in the wrong places? If it's a personal problem,
you can blame the holidays. But, if it's an aircraft issue, the culprit
is likely to be a weight and balance error. At best, overloaded or improperly
balanced aircraft experience degraded performance and handling. Large
errors can result in the loss of stability and control.
Running
the Numbers
This
B737-300 flight crew did not follow up on the first clue that the load
numbers were off. As the Captain reported, it took five more clues and
a firm landing to confirm their suspicions.
- The
load sheet was given to us for an on-time pushback and the First Officer
loaded the numbers in the Performance Computer and Control Display
Unit (CDU) per normal operations. No discrepancies were noted at this
time. However, I thought that the V-speeds seemed lower than what
they should have been (clue #1). The passenger count on the load sheet
and the flight attendant passenger count matched.... The takeoff...was
normal. We initially set the throttles at 90% and left them there.
This helped our takeoff performance but also probably helped hide
the weight discrepancy.... The First Officer informed me that the
aircraft seemed to fly as though it was heavier than we had calculated,
but he thought that the trim setting might have been a little off
(clue #2).... The descent was a little behind the profile required
to make the crossing altitudes (clue #3). We were having trouble slowing
the aircraft and getting it down on the approach with flaps 30-degrees
as briefed (clue #4). We elected to use flaps 40-degrees, but still
could not meet the stabilized approach criteria, so we asked for Runway
4. Tower was unable to give us Runway 4, so we elected to go around.
This probably helped our performance since the fuel used on the go-around
lowered our gross weight for the subsequent approach and landing....
On the second approach we both noticed that the aircraft was unusually
nose high for flaps 30-degrees and that more power than normal was
required to maintain our calculated approach speed (clue #5). We actually
flew ten knots faster than our calculated approach speed in order
to have better control over our pitch attitude. At one point during
the approach I noticed the stall indicator appear at the top of the
Heads Up Display (HUD) and then go away (clue #6). At this point we
knew that something was wrong, but even with all the clues we did
not know what it was. The approach ended with a hard landing. It finally
dawned on me that perhaps our weights were wrong on the load sheet....
When we checked the load sheet we realized that the agent had not
added the passenger and cargo weight to the OEW (Operational Empty
Weight) and had used the OEW as the Zero Fuel Weight (ZFW). This resulted
in a 22,000 lb. error in our performance calculations.
Heavy
Baggage
Failure
to account for the additional weight of passenger's "heavy"
bags can have a significant effect on the performance and control of
smaller aircraft. In the first of two ASRS reports that address this
matter, a Jetstream 41 crew wisely delayed their departure because of
suspicious indications.
- The
baggage loading and count was delayed and the baggage form got to
the crew late. Wanting to make an on-time takeoff, we completed our
calculations as quickly as possible.... While taxiing out to the runway,
the stall lights on the CAP (Central Annunciator Panel) momentarily
flashed on and off. This occurred twice during taxi. We referred to
the QRH (Quick Reference Handbook ) and rechecked circuit breakers.
No other indications occurred at this time so I assumed it was a malfunctioning
stall system. We decided to return to the gate to investigate. While
taxiing back, I noticed that the nosewheel steering was becoming intermittent....
When maintenance arrived, they indicated that the nosewheel was considerably
extended. I asked the flight attendant to move two passengers to empty
seats in the forward portion of the cabin. Maintenance indicated that
the strut had compressed some, so I decided to taxi back to the gate.
The nosewheel steering worked fine. At the gate...the First Officer
indicated that there was a 350 lb. error in his calculations of the
baggage.... Also, the ramp inspectors informed me that the baggage
count was correct, but some heavy bags were indeed "very heavy"
and were loaded in the aft end of the compartment.
This
ERJ 145 Captain's report on a heavy baggage incident was the subject
of a recent ASRS Alert Bulletin.
- The
baggage slip indicated that we had 2,204 lbs. of bags. At rotation
I noted that the trim setting was clearly incorrect and I had to push
the elevator to the forward limit to recover from the nose up pitch.
The aircraft seemed to be much heavier aft than calculated. After
arriving at [destination] the ramp personnel indicated that the baggage
seemed excessively heavy. The bags were weighed and the recalculated
figure put the cargo weight approximately 1,095 lbs. over the maximum
limit.
An
Alarming Takeoff
After
making mistakes that almost led to an accident, this C172 pilot generously
shared the experience through ASRS. It would be a mistake not to heed
the lesson.
- [I]
proceeded with the departure on a grass strip approximately 2,200
feet long. At 60 kts. I rotated and started to climb. I had packed
the plane and messed up because I had an aft center of gravity. Without
enough runway left to put down, I climbed (with the stall warning
screaming) to avoid trees at the end of the runway. [I] just cleared
the trees. The contributing factors were too much baggage, not knowing
the density altitude, and complacency. Thank God I am still around
to share this lesson.
Holiday
Hints
Holiday
pressures can affect concentration and judgement. Three ASRS reports
offer some valuable lessons about this seasonal syndrome.
Just
after an airport "turnaround" (from south to north oriented
runway operations), this A310 flight crew was given clearance to cross
an active runway enroute to the assigned runway. The Captain picks up
the story as they approached the hold short line of the intermediate
runway.
- I
immediately saw a DC10 on short final for Runway 27 and slammed on
the brakes.... We did encroach slightly on the Taxiway B to Runway
27 hold short line.... The DC10 did not appear to take any evasive
action.... I strongly suspect that there were considerable distractions
for the controllers associated with turning the field around from
southerly to northerly operations. "Habit patterns for survival"
saved the day. That is: 1. There were no distractions (e.g. no Flight
Management Computer programming) prior to crossing the active runways,
and 2. Good aircraft alignment and lookout facilitated properly clearing
both left and right before crossing active runways and taxiways.
This
was quite a jolt, even for an experienced and proficient Captain
and reinforces why we do things the way we do. A piece of wisdom
(from a 40-year airline veteran) came to mind as I reviewed these
issues, "It's the holidays, and people don't concentrate like
they do at other times."
Several
reports in the November 2003 Callback (#290)
addressed the problem of unplanned flight into Instrument Meteorological
Conditions (IMC). Another report on this dangerous practice offers a
timely lesson: Don't let the pressure to get home for the holidays cloud
your judgement.
-
I departed in VFR conditions with a weather
briefing from the Flight Service Station (FSS) forecasting VFR to
Marginal VFR along my route of flight. After climbing through scattered
clouds, I leveled at 8,500 feet MSL. Near my destination, the layer
below closed and I found myself on top of an overcast. By that time,
ASOS at my departure point was also reporting overcast (the flight
distance was only 80 NM). Weather was clearly building in all directions.
I proceeded to a point above terrain well known to me and descended
through clouds to approximately 1,000 feet AGL, where I broke out
[and landed] at a nearby airfield.
The
weather was forecast to worsen in the direction of flight. When
it became clear that I would be unable to proceed VFR under the
clouds with sufficient altitude above the ground, the appropriate
decision would have been to return to my departure point immediately.
I felt pressed to get my errands done and get home for the holidays,
and this affected my judgement when I decided to climb above and
continue the flight. I have instrument training, but have not yet
been rated.
Holiday
fatigue and haste contributed to this private pilot's runway incursion.
- After
landing on Runway 36, I was instructed by Tower to make a right turn
on the next taxiway and hold short of Runway 6.... My attention was
not where it should have been. I was concentrating on the distant
taxiway and ramp lighting and on my desire to finish this flight and
return to my home base. As a result of my lack of attention, I proceeded
to cross Runway 6 without clearance and with an aircraft on final
for Runway 6. I was immediately advised and admonished for my error....
I was tired due to the holidays and my personal workload... As the
saying goes, haste makes waste....
From the Maintenance
Desk
ASRS
continues to receive reports concerning B767 wheel spacers. (see Callback
#282, March 2003). The following two reports shed some light on possible
causes for spacer problems on the nose gear.
-
Even with the proper manuals and paperwork on hand, the spacer on
the B767 nose wheels seems to be a trap. It continually sticks to
the wheel bearing when the assembly is removed from the aircraft.
The 767 has the only nose wheel spacer of [my airline's] fleet types.
This and the fact that B767 tires are rarely changed at this station
contribute to the spacer being missed.
-
I was notified by my supervisor that an axle spacer was found to be
missing on the right side nose tire during the walk-around inspection....
On the B767-300 there are two different axle configurations. One is
internally threaded and the other is externally threaded. I did not
think the externally threaded axle required a spacer.
According
to the air carrier's maintenance manual, wheel spacers are required
on both the internally and the externally threaded B767 nose gear axles.
