Too Heavy to Fly

[Rose Pink]

.... Perhaps the pilot of the affected aircraft taxied across a scale or his aircraft is equipped with monitors that alert to an overgross situation. Customarily the 1st officer programs the flight computer as the aircraft is enroute to the active runway while the pilot is at the controls. The computer wouldn't be aware of the overgross until it was away from the gate.

Get over it! ...

Thank you for the explanation. I can "get over it" when I understand what happened.

 

[Rose Pink]

Is there a specific question here? If so, perhaps I can shed some light..

Yes, I've asked several specific questions in this thread. To reiterate, they are:

1. Why was this flight different than the other flights that DH has taken under the same conditions (same aircraft, same airport, same destination, same weather)?

2. How do the airlines determine weight? At what point do they know (or estimate) the weight?

3. Why aren't these things known prior to taxiing to the runway? (Is it what Jim suggested about driving over a scale after leaving the terminal?)

Thank you.

 

[Carl D]

Yes, I've asked several specific questions in this thread. To reiterate, they are:

1. Why was this flight different than the other flights that DH has taken under the same conditions (same aircraft, same airport, same destination, same weather)?

Without knowing the precise conditions, it's imposible to say for certain.
I will say that a single degree warmer temperature can mean DRASTIC perfomance change.

2. How do the airlines determine weight? At what point do they know (or estimate) the weight?

Airlines are approved for an average weight program. The weights used are just that... "average weights". Same with bags.
On our aircraft all females in the summer weigh 174 pounds. When the calander turns to November 1st, they gain 5 lbs and become 179. Guys weigh 15 pounds more, but kids under 12 always weigh 80 lbs. Bags weigh 30 pounds each.
It sounds imprecise, but in totality it's probably pretty accurate. The aircraft can handle any small deviations.

3. Why aren't these things known prior to taxiing to the runway? (Is it what Jim suggested about driving over a scale after leaving the terminal?)

Sometime to expedite the operation the airline will "get their numbers" as they taxi. Other times the temperature may climb a couple degrees between the dispatch release, and reaching the runway.

Thank you.

Just a side note--
All these take off distances are predicated on the worst possible scenario.
For example, under normal conditions the aircraft may need 4,000 ft of a 12,000 ft runway to depart.
However, several contingencies are looked at:

- Can the aircraft accelerate to V1 (takeoff decision speed), and then abort the take off, and stop in the remaining runway?
- Can it accelerate to V1, lose an engine, and continue to accelerate to Vr (rotation speed), then cross the departure end of the runway at a minimum of 35 ft.
- Can the aircraft climb at a minimum of 200 ft per mile with one engine inoperative? (or more if terrain dictates).

If the above examples can not be achieved, weight must be reduced.
These are just a few examples of what happens that the passenger will (hopefully) never see.

Feel free to ask more questions if I didn't explain adequately.

 

[x3 skier]

To add what Carl D very well explained, if you ever heard the Cockpit Crew tell you over the PA, "We are waiting for the final paperwork", they are waiting for the final bag/passenger count so they can compute all the distances required for takeoff, etc. if dispatch has not already done it for them.

High Altitude airports are OK on "Standard or Cold Days" but when it gets hot, takeoff performance rapidly decreases.

BTW, if anyone asks me my weight, I always tell them I am a FAA Standard Passenger.

Cheers

 

[Rose Pink]

Feel free to ask more questions if I didn't explain adequately.

You did great, Carl. Thank you. It is the temperature that has DH and I stumped as the temp that day is not unusual for our climate--sometimes it is even hotter. That coupled with all the hundreds of flights over the years in similar conditions and this is the first time he has ever experienced this. We never questioned the airline's decision but couldn't figure out why "this time" was different. I guess we won't know for sure.

 

[Carol C]

I don't blame the airlines one bit. This is to be expected with the alarming increase in obesity in the "Western" world (and even in children) and the concurrent historic rise in fuel prices. I don't blame the airlines for charging for extra luggage either. Have you ever seen the boxes of tvs and other heavy consumer electronics that passengers carry through MIA, for example?

Something's gotta give. Just be glad they're still giving vouchers to folks who volunteer to be bumped.

 

[pwrshift]

I haven't heard of this in years. I can remember on a short 1 hour flight in a small jet, maybe 20 years ago, being asked to move to another seat to balance the plane but that was it. Made me feel singled out and promptly went on a diet - that didn't work for long as the planes got bigger.

Brian

 

[T_R_Oglodyte]

I haven't heard of this in years. I can remember on a short 1 hour flight in a small jet, maybe 20 years ago, being asked to move to another seat to balance the plane but that was it. Made me feel singled out and promptly went on a diet - that didn't work for long as the planes got bigger.

Brian

About three or four years ago I took a bump on a late afternoon Alaska Airlines flight out of Las Vegas during a heat wave. Plane was sold out, and they had to send it out with about ten empty seats because of reduced lift.

When we lived in the San Bernardino Mountains it seemed as if every summer a private plane would crash at the Big Bear airport while attempting a takeoff during a heat wave. That airport is over 6500 feet elevation, and during a heat wave summer temps in the Big Bear Valley will often be in the mid-90s Fahrenheit.

Humidity is also a factor. Humid air is less dense than dry air (at the same temperature and elevation), so planes loss some lift due to humidity. The humidity effects, though, are not as large as temperature and elevation effects.

Density Altitude...You're Higher Than You Think!

 

[Rose Pink]

Density Altitude...You're Higher Than You Think!

From the above link:
The worst case remembered involved a Cherokee 140. It was a hot afternoon when three large men climbed aboard and attempted a takeoff in 1988. Eyewitnesses said later the craft climbed fifty feet above the runway, then sank. The pilot pulled back on the yoke and the plane would temporarily climb, then sink again, not ready to fly. Finally, he pulled the nose up so high, barely clearing the trees, that it rose almost vertically, then stalled and spun into the ground. Only the pilot survived the crash.


Obesity (even overweight) causes increased morbity and mortality due to heart disease, diabetes and cancer among other ailments. Now we can add it as a contributor to plane crashes. Guess it's time to get serious about my diet.