Global Aviator South Africa - May 2018

14 Vol. 10 / No. 5 / May 2018 Global Aviator

should be used. An example would

be a large group of athletes, or a

rugby team. The crew of flight 1285

predicted that the weight of each

passenger + baggage was 170 pounds

just like it is set out in the guidelines.

For a regular commercial flight

consisting of a mixture of people

• men, women and children, this
  would be 100% correct, but remember
  this was no ordinary flight. All the
  passengers were male adults.

Could this be a mistake?

The investigators actually went and

took a look at the medical records

of the passengers, to get their actual

weight. So a more realistic weight

would be for instance 220 pounds

per passenger (including baggage

and equipment they had). With the

new estimated weight, the passenger

weight was calculated at more than

54,000 lb. – that’s 12,000 lb. heavier

than what was recorded on the load

sheet. The load sheet had the passenger

weight as 42,499.2 lb. It should be

remembered that, with the exception

of the take-off fuel, the flight had

been flying with the recorded weight

all night, from Cairo and Cologne

without any problems. So could the ice

in Gander have made a difference?

With all this in mind, investigators

strongly suspected that a combination

of ice and extra weight could have

prevented the DC-8 from staying in

the air. But because no one in Gander

actually saw ice on the wings, this

was just a theory. So investigators still

had some investigation to do. Some of

the other aspects that they looked at

included the engines and also the aircraft

stall. All four of the airplane’s engines

were found at the wreckage site and sent

away for further investigation. There

was rotational damage on all four of the

engines – which means that the engines

were running when they hit the trees.

The damage patterns that were

observed in the number 1, 2 and 3

engines were consistent with ground

impact at a high rotation speed. Each

engine had ingested debris during the

impact with the trees and ground, but

none displayed any physical evidence of

pre-impact distress. It was determined

that engine 1, 2 and 3 were operating

at high-power settings when it hit the

ground. The number 4 engine was

determined to be operating at a lower

rpm than the other three engines when

impact occurred. However it could

not be determined whether this lower

ground impact rpm was the result of

the ingestion of debris as the plane went

through the trees just before impact or if

it occurred prior to descent into the trees.

When performance simulations

were conducted, it was indicated that

the performance of the aircraft could

be explained by the one engine losing

thrust together with the performance

degradation that was a result of ice

contamination on the wings. When it

comes to the aircraft stall, we know

that the lift produced by a wing is

primarily dependent on three things:

wing geometry, angle of attack and

airspeed. The wing (airfoil) geometry

is altered through the use of trailing

and/or leading edge flaps. Typically,

when you extend the flaps, it increases

the lift-producing capabilities of the

wing. The angle of attack can be

described as the relative angle between

the air impinging (air flow) on the

wing and the wing chord. Another

way to describe it is to say that it is

the angle between oncoming wing

and a reference line on the wing.

As the angle of attack increases,

so does the coefficient of lift. The

point at which an airplane will stall

depends on the angle of attack. Let’s

say for example that with flaps set on 18

degrees and the weight of the aircraft is

344,500 pounds, then the FAA (Federal

Above: Some of the wreckage that was found.

Left: Mortar shells and charred weapons

recovered from the wreckage.

Airline accidents