Plane Answers: Paying off passengers on weight restricted flights and a question about approach speeds

by Kent Wien on

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!

Kent,

My girlfriend and I were traveling to Washington D.C. on Delta from Des Moines via Cincinnati. At CVG, the ticket agent said they were looking for volunteers, as the flight was oversold. I eagerly rushed up, since we were just staying with a friend that night, and inquired. He offered $600 each, meal vouchers and a hotel for us. He said there was an issue with weight as well.

We hung around the gate to make sure, and at the last minute, he said “Captain’s ordered everybody on.” The flight was full. Very full. We were the last two seats on the CRJ. My girlfriend had to sit next to the FA in a jumpseat/lavatory door.

My question is: How can weight play an issue? Aren’t they fueled according to the passenger count? How much does luggage weight come into fuel calculations? And lastly, What could have made the pilot change his mind about weight?
I would have jumped at the $600 offer. You were smart to try and nab it.

Very often, flights are weight restricted, which means that after the safe fuel and reserves are added to the flight, there’s only so much weight left over for the passengers and bags. This is more common on the regional jets, but it occasionally happens to the smaller Boeings and MD-80s.

As the boarding is taking place, there are often a few variables that aren’t apparent until the baggage, freight, mail and fuel are added to the airplane. Getting an up-to-the-minute tally of the weights allows the load planner (which may even be the pilots, depending on the airline) to get the maximum number of passengers and bags on the flight. Baggage weights aren’t actually weighed, however. Average weights are used; 30 pounds domestically and 40-45 pounds internationally.

You’re also more likely to run into this situation when the weather is poor at your destination, since the flight plan will need to include enough fuel to travel to an alternate airport after reaching the destination just in case the weather isn’t good enough to get in. So this added fuel reduces the useful load of the airplane. Each gallon of fuel weighs just over six pounds, in fact.

Occasionally, there may be a similar weight restriction based on the maximum landing weight of the airplane. If the airplane must operate again with nearly full fuel, and the distance isn’t enough to burn down below the maximum landing weight, the number of passengers will also need to be restricted.

Clearly it was in the airline’s best interest to look very closely at the numbers, something that can only happen at the last minute, to see if they could get you on. But they didn’t want to find themselves in a situation where at the last minute they’d have to remove two passengers and their bags and delay the flight if the weights came in just over the maximum allowed. So in your situation, they held you two back just in case they needed the weight reduction. I’ve also been in your situation when flying on another airline and just as I was starting to spend the extra cash in my mind, the door opened up we were rushed on at the last minute.

Tom asks:

Hi Kent,

You said that the newer 737-800s are “faster” on final approach than the older 737s. If the flight crew controls the airspeed on final approach then wouldn’t the speed on final be the same regardless of the age of the 737? Please explain and many thanks.

I should have been more specific. You’re right, the age wouldn’t have any impact on the speeds, but the older 737 model, the -200s are able to approach much slower than the -800. Another significant influence is the weight of a particular aircraft which can change the approach speed by twenty to twenty-five knots (23 to 28 m.p.h.).

In a previous Plane Answers, I called a lot of friends who fly a variety of airplanes and they provided me with the approach speed of a variety of airplanes. You’d be surprised which airplanes land the fastest:

747-400: 157 (174 m.p.h.)
737-800: 148 (170 m.p.h.)
A380-100: 145 (166 m.p.h.)
767-300: 142 (163 m.p.h.)
A320: 142 (163 m.p.h.)
EMB-145: 139 (160 m.p.h.)
777-200: 138 (159 m.p.h.)
MD-80: 136 (156 m.p.h.)
A300: 135 (155 m.p.h.)
A319: 132 (152 m.p.h.)
757: 132 (152 m.p.h.)

Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he’ll use it for the next Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work. Twitter @veryjr

Plane Answers: Whistling airplanes and heavy passengers that cost airlines more in fuel?

by Kent Wien on

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.