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Plane Answers: Whistling airplanes and heavy passengers that cost airlines more in fuel?
Welcome to Gadling's feature, Plane Answers, where our resident airline pilot, Kent Wien, answers your questions about everything from takeoff to touchdown and beyond. Have a question of your own? Ask away!Julie asks:
Hi Kent!
Last week on a flight out of ATL on a CRJ during takeoff there was a high pitched sound that got higher and higher until it eventually stopped as we climbed up near the clouds. There was a thunderstorm passing through Atlanta so the plane was wet, I was wondering if the noise had to do with the moisture on the outside of the plane? It was noticeable enough to make me look up for a second, but it disappeared pretty quickly.
Do you know what it could have been? I think every time I fly (although not that often) I come up with a new question for you! I love reading this feature every week, thanks!
Thanks Julie,
I'm pretty sure what you were hearing was a door seal that had just enough of an air leak to cause it to whistle. As you climbed the cabin fully pressurized, which must have stopped the noise.
We occasionally see this in the cockpit around the windows. If it's too annoying, maintenance will pressurize the aircraft on the ground to find the source of the leak. This leak isn't really a safety issue, but if it's annoying enough to the passengers or crew, then it really needs to be fixed.
Diana asks:
Hi Kent,
My question has probably been asked a thousand times but I've only had to ask this of myself recently because of an argumentative essay I'm writing on overweight people being charged extra for airfares.
I saw your comments on a plane's fuel plan which talked about the factors needing to be considered when designing the fuel plan. These included the forecasted winds of an aircraft's journey, the altitude the aircraft will be flying at and the weight of the aircraft.
Do you think that it would be correct to assume that the heavier the plane is, the more fuel the plane will need to be operational?
Also, if the weight of the plane was too heavy, could that cause a safety risk? Yes it may sound 'obvious' to some (if in fact the answer is 'yes') but I just thought I'd ask for confirmation.
Thanks a lot.The answer is a definite yes.
Let me give you an example:
We're encouraged to NOT take unnecessary amounts of extra fuel. We're told that it takes an extra 10% of the weight of the added fuel just to carry it along on average.
So our airline has also reduced the amount of water carried on board for the lav sinks to the bare minimum. That has saved about 40 gallons of water on the 757, or 240 pounds per flight.
As for safety, that'd be a hard one to argue. The FAA doesn't require airlines to weigh each passenger, but uses a system of average weights for each passenger of 190 pounds in the summer and 195 in the winter.
Thanks for the great question, Diana.
Do you have a question about something related to the pointy end of an airplane? Ask Kent and he'll try to use it for next Monday's Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.
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Reader Comments (Page 1 of 1)
Ted Jun 1st 2009 12:56PM
Although passengers' weight might not be a problem at all on a medium to large jet (think Boeing 737 and 747) it may become a major challenge for a small aircraft.
Why is that? For one thing a bigger jet isn't always loaded at maximum take-off weight, especially now with the accent being shifted on less weight=less fuel needed, and secondly, even if it were filled to the maximum, a big airplane still has a pretty big margin of safety i.e. could easily cope with let's say an unaccounted 1000 pounds extra weight of passengers (for a 747 that's being 0.1% overweight).
A smaller airplane on the other hand (think commuter props like the Beechcraft 1900) has a very small margin of error - it carries a maximum of 19 people and if you have a load of people that are on average 240 lbs instead of 190 you suddenly have almost 1000 lbs of unaccounted extra mass, which adds an extra 5.5% of the maximum take-off weight. So the same 1000 pounds mean 55 times MORE extra weight in percentage for the small aircraft than for the big one - it's obvious how that can present a huge problem.
Moreover, think of how all this weight is distributed in a plane. When it comes to big airplanes, the passengers' weight distribution is roughly even throughout the plane, however, think of what this means to a small airplane. Imagine you have 10 people that are 140 lbs each and 9 that are 250 lbs each; that means some 3600 lbs for 19 passengers, so on average you have 192 lbs/person, close to the airlines' assumptions; hence the plane won't be overweight. Now think what happens if all the 250 lbs people sit on the right and all the 140 lbs ones stay on the left of the plane? You get a plane which is unbalanced with the right hand side being significantly heavier than the left.
But what if you put all the heavy people in the front? You get a nose-heavy aircraft, which will have big trouble lifting off the runway and will tend to go nose-down every chance it gets. And what if you put the heavy people all in the back of the plane? It will be so tail-heavy it will probably end up with the nose in the air even before starting the engines. But if it takes-off this nose-up attitude can stall and crash the airplane.
And for a definitive answer, Air Midwest flight 5481, which was a small commuter airplane like I described above, was some 600 lbs overweight when it crashed - and the accident report decided that this was one of the major causes of the crash - so, weight it definitely is a major safety issue.
Safe flights!
Jim Jun 3rd 2009 7:42PM
Flying on smaller aircraft you will be weighed. I have flown a bit around the Solomon Islands on the ever reliable and tough Twin Otter and you are weighed together with your bags.
Perhaps it will become cost effective for airlines to have some sort of discrete weight check of passengers so a more accurate figure can be calculated.
Kent Wien Jun 3rd 2009 8:57PM
Thanks Jim,
Ironically, I spent many hours flying the Twin Otter in Alaska:
http://www.youtube.com/watch?v=3BL_jT5y-uE
And yes, I probably should have mentioned that we weighed (or at least asked the weights of) our passengers.
And, as Ted mentioned, we did that because it is a bit more critical on the smaller aircraft.
You guys always keep me honest!