September 1, 2012

"Waiting for Numbers"

I included this picture as part of a earlier post and thought it warranted a little more explanation.  What you see below is the "load closeout" that I saved from a recent flight from Dallas, Ft. Worth, Texas (KDFW) to San Jose, California (KSJC).  Anyone who has ever monitored the ground control frequency at a major U.S. airport has heard one of our pilots inform the tower that he was "waiting for numbers."  


This little piece of paper is quite important and tells the pilot everything he needs to know regarding weight and balance.  The weight part of the equation is simple.  The aircraft must weigh less than the max ramp weight before the brakes are released for taxi.  It must weigh less than the max structural takeoff weight before takeoff (this number may be further restricted by factors like runway length and environmental conditions), and the aircraft must weigh less than max landing weight before landing.

Balance all comes down to the location of the CG or Center of Gravity.  Go get a 2X4 out of your garage and balance it on the tip of your index finger.  It might take a while to find the right spot, but when you support the board from the CG, it will balance on the tip of your finger.  Now put a can of soda on one end of the board.  The CG of the board has now moved and you must move your hand to the new CG or the board will fall.  Balance on an aircraft works exactly the same way, except that mistakes lead to much more serious consequences (see below).

Oops...sometimes the CG is even important WHILE loading.
As important as all this is, an aircraft doesn't have to be perfectly balanced.  That is, the CG doesn't have to be right in the middle.  The CG does, however, need to be within a pre-determined range.  Load the aircraft nose heavy and the pilot may not be able to lift the nose during takeoff.  Load the aircraft tail heavy and aircraft could be unstable and potentially difficult if not impossible to control during a stall.  I won't bore you with a full explanation of the CG and its affect on both stability and control, but feel free to click HERE for more detail.

Back to the "load closeout."  At many, if not most airlines, the pilots have all the weight and balance data they need to legally takeoff before the door is closed for departure.  However, at some airlines, mine in particular, this data is transmitted to the pilots and printed in the cockpit during taxi.  Below is a line by line explanation of the closeout.

Line 1)  The aircraft tail number: N9420D. The message was transmitted through the DFW station to the aircraft.
2)  Load Closeout revision number 00 indicates that this is the first closeout sent for this flight.  The closeout was transmitted at 1008L time.  3)  Flight 1347 from DFW to SJC.  The nose number for the aircraft was N4WY. Airlines often use "nose numbers" as opposed to "tail numbers" to internally track aircraft.
4)  Takeoff Weight:  148,867 lbs.  The max takeoff weight for this aircraft is 160,000 lbs, so we were well below the limit.
5)  Fuel On Board:  34,052 lbs.  The "A" represents an actual fuel load that I manually sent to our load planner as opposed to a "P" indicating a planned number.
6)  Zero Fuel Weight:  114,815 lbs.  Well below the limit of 122,000 lbs, the ZFW represents the weight of the loaded aircraft minus fuel.  Note that the FOB + ZFW = TOW.
7)  Flap setting / Stabilizer trim.  The flap setting required for takeoff depends on the runway to be used.  In this case, we departed from runway 18L, which required flaps set to 6 degrees and a stabilizer trim setting of 5.4.  I like to draw a line from the flap setting to the stab trim number to help the Captain identify the correct information during his pre-takeoff briefing.
8)  Center of Gravity: 14.4%.  Described in percent of MAC ( Mean Aerodynamic Chord).
9)  Passenger count:  140 passengers.  0 cockpit jumpseaters.  0 cabin jumpseaters.  I wrote the number 145 to indicate 145 souls on board.  140 passengers plus 5 crew members.  This is an important number to be transmitted to ATC during an emergency.
10)  Child count: 5.  Included to inform the pilots that an appropriate child weight was used to account for 5 of the 140 passengers listed above.
11)  Passenger weight:  23,085 lbs.  The number used to account for each passenger varies depending on the time of year.  Passenger weights are higher during the winter to account for the extra weight of winter clothing.
12)  Cargo weight:  3,180 lbs.
13)  Empty Operating Weight:  85,550 lbs.  The fixed empty weight of the aircraft before fuel, passengers and cargo.
14)  SECOK.  Indicates that all security checks are complete.

Sending this data during taxi helps facilitate an on-time departure, but there are a few drawbacks.  First of all, receiving, interpreting and setting the information included in the closeout requires the attention of one set of eyes.  During taxi, both pilots should pay attention to aircraft movement and should minimize any head-down activities.  So the closeout is an unfortunate distraction during a critical phase of the operation.

Secondly, as the title of this post suggests, we don't always get our numbers before we get to the end of the runway.  As a result, you will often hear pilots inform the tower that they are "waiting for numbers."  This is usually caused by one of two things.  Either the gate agent neglected to enter final passenger numbers or the ramp crew forgot to enter final numbers for baggage and cargo.  Either way, the load closeout cannot be issued if any part of the puzzle is missing.

On one especially frustrating night, I sat near the end of the runway for a significant amount of time waiting for the closeout.  After some time, I called our load planner...a third person in the process who does all the pre-flight load planning...and inquired as to the delay.  Turns out our flight had been the gate agent's last flight of the night.  After closing the door and seeing us off, she left for the day but forgot to input the final passenger numbers.  Someone finally reached her on her cell phone and asked her to come back to the airport to complete her duties.

So the next time you're sitting at the end of the runway, watching other flights taxi by and takeoff, chances are you're "waiting for numbers."

4 comments:

  1. As a ramper, I've seen the effects of a "wheelie". Major No Fun for the flight crew.

    There are aircraft I've loaded (like the DC8) where we were very careful to keep the weight forward to avoid a "wheelie".

    ReplyDelete
  2. Great idea to 'splain the "Waiting for Numbers" gig. When we went to ACARS, I always joked, "Now I feel like a REAL airline pilot--I get to sit at the end of the runway and 'Wait for Numbers' like everyone else!" LOL!!

    ReplyDelete
  3. Doesn't ATC tell the crew / airline off for being late in such a case ? I could imagine creating a tailback just becasuse data is missing. I am quite sure that here in Ams you won't get push back unless all parameters, including the loadsheet etc is present.

    ReplyDelete
    Replies
    1. Depends on the airport Mike. For instance, at DFW there is ample room at the end of the runway for a jet waiting for numbers. At airports where room is scarce, it is expected and sometimes mandated that aircraft do not call for taxi until all numbers are received.

      It is relatively unusual to experience the delays I describe in this post. It is most common to receive the closeout numbers during push back.

      Delete