Bagram 747 CG shift with increased fuel
 

I am wondering how much different the cg would have been for the takeoff out of Bagram vs the earlier takeoff en route to Bagram? It is my understanding that the Bagram takeoff was with a heavier fuel load. Could that difference have contributed to the appearant difficulty keeping the nose from pitching too high?

What do you think crews/dispatchers do with trim calculations when the fuel load changes (every trip)?

Of course, the calculated trims accuracy depends upon the actual load and fuel being of the same weight and in the same positions as used in the calculations.

BOAC and Onceapilot - thanks for the responses. I know that a proper weight/balance determination is made for every takeoff and should have caught the cg being out of range if it was. I am just trying to identify any possible contributing factors to the puzzling detail that the the takeoff heading to Bagram went off okay while the one out of Bagram led to the accident. From what I have gleamed from the discussion here, the only significant weight/balance change between these two takeoffs was more fuel for the second.

Is it possible that the weight/balance determination for the first flight was incorrect, but that with less fuel the cg was in an acceptable range? If the same, incorrect, cargo weight/distribution data was then used prior to the ill-fated takeoff it might have shown the cg to be within range with more fuel when it actually was not.

- at this stage, for we armchair QBs MANY THINGS are possible, some things are more likely.

As a matter of curiosity I was wondering how far out of range the C of G would have to be before a 744 tips back onto its tail on the ground.

Anyone know?

About 41-42% MAC. The aft limit being 33% MAC.

The Korean -400F with the loadsheet error, landed with 40.2% MAC. Its nose wheels were not touching the ground anymore when the aircraft came to a full stop.

B-HKD - That's sobering to get the W/B that far off.

I've loaded aft CG where the nose wheel extends a little bit but to imagine it being off the ground is just amazing to consider. Can only imagine how it flew.

Just to go off on a tangent slightly with regards the Korean Air 747- if you discovered whilst in the air that your fuel load was way off, is it possible in a 747 to select a certain combination of tanks and bring the aircraft closer to correct trim by burning/ dumping fuel?

the -400F -400BCF (as involved in the Bagram accident) -400BDSF -400ERF do not have activated stab tanks. So thats out of the question.

As the center tank quantity decreases and wing fuel from the main tanks (wings) is burned off, the CG continues to move aft.

Landing ASAP before it gets worse comes to mind.

Had it not been for the crew of the Korean -400F contacting load control at HQ in Seoul, immediately after takeoff and them telling the relief pilot and captain to go downstairs to move pallets forward, the plane would have landed with more than 43.7% MAC CG. Some 10.7% aft of the limit!

Considering the CG was 37.8% MAC at takeoff (4.8% aft of the limit) and not including the subsequent load shift by the crew, the resulting fuel burnoff to Seoul would have resulted in a CG shift of 5.9% MAC.

Amazing that HQ advised them to continue or that the captain didnt just land immediately at Oslo overweight with a CG 4.8% MAC aft of limit instead of the 7.2% MAC aft of limit at Seoul. Again, land ASAP comes to mind.


In the case of the National -400BCF, the aircraft was obviously not airborn anywhere near enough time for a burnoff of center tank and most of the wings to result in the CG moving AFT.

Yep.
Too nose-heavy move fuel out of the centre wing tank and/or tanks 2/3.
Too tail heavy move fuel out of tanks 1/4.

I assume this involves burning fuel directly from the tanks you mentioned, and not actually moving it elsewhere correct? (Via 1&4 and 2&3 xfeed)

You could use the Fuel Transfer Main 1 & 4 switch to move the C of G forward.

Creative fuel pump selections with all the X feeds open using the jettison system would get the C of G aft quickly but only to a point system logic would cause reserves to tranfer as normal moving the c of g forward or stabilizing it, you could stop the jettison and continue to "burn" the c of g aft again with x feeds all open and creative fuel pump selections.

After rechecking the video at the 1 second mark after the 747 enters view.

At that instant in time I get a pitch of 43 degrees with a standard deviation of 2 degrees for 5 close snap shots.

The 747 is at 970 ft agl and 4400 ft away from camera (along ground). The 747 is 7800 ft from the T/O threshold (along ground) of the 11819 ft runway length.

If you have doubts please do your own calculations and let me know your numbers.

- Use the best video available.
- Google Earth
- Google Maps
- Airport map
- Most good video players
- Any decent Photoshop software
- 747F dimensions (Boeing)
- Get meters/pixel (object dependant)
- Get degrees/pixel
- Trigonometry

This has come from a reliable source:-



FYI, I'm in IBT Go-Team training in DC with NTSB and others, and Director of NTSB Office of Aviation Safety briefed us on this accident today. This is accurate info from NTSB source today:



The CVR/FDR on the accident aircraft stopped working on rotation; engine/fuselage/tail parts were located on the runway. A total of (7) MRAP armored vehicles were being carried as cargo. NAC was the only civil DoD contract carrier who will carry these vehicles. Aircraft loaded at Camp Bastian, not Bagram, was stopping in Bagram for fuel. Aircraft uplifted 48,000 lbs of fuel at Bargram for flight to DXB. After impact, 1 MRAP vehicle was deeper in the impact crater than any aircraft/fuselage parts.

Huh??
What would that be from? tail bounce on take off?? (Hmm, damage to elevators/horizontal stab? Would not some of the eyewitnesses previously cited have mentioned this?
Different from some folks who have carried that cargo and their inputs in the currently locked thread at R & N. .
??? Is this deemed significant?
Consistent with previous info ...
Not sure of significance.

It will be interesting to match this leak with the reports that are eventually issued by NTSB in support of the local authorities.

That C of G info is quite illuminating, as I suspected.

What it indicates is that if the accident was caused by a C of G problem it was one that occurred at the very least after line-up and not on loading which makes the cargo shift theory look pretty compelling. Given the nature of the cargo there can't be much chance its anything else but an unsecured vehicle probably setting off a cascade of runaways.

False.



False again.

Cant fit 7 MRAPs in a -400BCF or any onther -400 freighter.

World manages 6 with some clever loading.

The majority of other carriers load 5.


Pretty safe to say this 'reliable' source and the alleged information leaked from the briefing is pure BS.

Just out of interest. I thought all power was removed from the cargo PDU's with engines running and certainly in the air. Maybe some superhuman strength kicked in when the panic struck?:uhoh:
A fully loaded pallet is not easy to shift, especially if the base is distorted.

B-HDK: given the options, I'll lay my betting money on your estimate. ;)

Interesting!
Just out of curiosity I was tempted to do some rough guestimates/calcs.
Don't shoot me for it this is not meant to speculate on the cause, just checking some plausibilities and orders of magnitude.

So let's have a look:
Mean aerodynamic chord of the 747 is 327,8 inches. (http://www.boeing.com/assets/pdf/com...misc/A20WE.pdf).
7% of that would mean 22,95 inches. (Korean managed to take off with ~38% so let's assume KAL + 2% for a likely unrecoverable config for takeoff).
So the Cg of the aircraft would have to be ~23 inches behind the aft Limit in a case where the front wheel almost lifts off the ground.
If we assume a TOW of roundabout 300.000kg an MRAP weight of ~12000kg a single MRAP would havce to shift a whopping 573 inches to get that sort of Cg shift.
If we instead assume they added 25.000 kg of fuel that would require the added fuel to be stored ~275 inches behind aft Cg to achieve the same shift.
Question to the 747 experts: Is that technically possible?

Anyway These rough calcs give me the Feeling there is really a massive load shift required to get into a seriously tail heavy config. And the KAL was still able to land safely.

The more one looks into it the more puzzling it gets.

747 Fuel loads index change (rounded).

Up to 53,000kg virtually 0 index change. (All main tanks filling).
53-65T moves forward 25 units. (Inboard Mains 2 & 3 filling).
65-73T moves aft 60 units. (Reserve tanks filling).
> 73T keeps moving forward. (Inboard Mains 2 & 3 filling and centre @ >110T).

Tankering of fuel in the centre tank on the previous sector may have masked an out of C of G loading, if this was redistributed during the stopover it may have left the A/C outside the C of G limits. (Removal of 25T from the centre wing tank would result in a rearward C of G change of almost 200 units.

However any load error during refueling would have been picked up by the A/C and generated a "> STAB GREENBAND" EICAS message which comes from the nose gear pressure switch during final prep indicating an error in any of the following, Loading, Weight, C of G.

After checking the video for the 1st 5 seconds after the 747 enters view. From 5 snapshots I get:

188 kts true path-velocity (not indicated speed)

Altitude 970 ft AGL (stdev 26) (minimal climb)

V/S 510 ft/min (minimal climb)

2 deg flight path (minimal climb)

36 deg pitch (stdev 4)

32 deg AOA (stdev 5)

At the moment the 747 enters view the 747 is 4600 ft away from camera (along ground). The 747 is 8500 ft from the T/O threshold (along ground) of the 11819 ft long runway.

If you have doubts please do your own calculations and let me know your numbers.

- Use the best video available.
- Google Earth
- Google Maps
- Airport map
- Most good video players
- Any decent Photoshop software
- 747F dimensions (Boeing)
- Get meters/pixel (object dependent)
- Get degrees/pixel
- Trigonometry

Anyone else get the email from the FAA safety advisors this week? Urgently communicated review of techiques used to secure heavyweight vehicles into cargo aircraft.

As an illustrious "American" politician has said: "What does it matter"?...The investigation will give the answers soon enough...

On thing I find interesting regarding all of the speculation from the armchair pundits who consider themselves signifantly informed, is why, oh why, has the subject of degraded flight controls (as in jammed elevator, hydraulic loss, mechanical failure) crossed these pages?

That's why we are not the investigators...We have tunnel (load shift/CG problem) vision...:ugh::ugh::ugh:

Because if you read the topic of this post it says Bagram 747 CG shift with increased fuel. :ugh:

Or is that not clear?

Who knows maybe they landed hard and the cargo became unsecured. We know adding fuel wouldn't do that to the aircraft on climb out. We also know that slat retraction issues have happened. It's also a war zone and If I had a first guess I would hazard sabotage of some sort. Not hard for a ground crew to cock up that aircraft, especially with airline crews that don't do walk arounds. For all we know they weren't producting enough power as well. When I ponder a load shift, it happened to Emory in Sacramento. What ever the case, someone dropped the ball, didn't do their jobs.

　

Quote:

---

DownIn3Green, on May 23rd, 2013. ... The investigation will give the answers soon enough...

---

QUESTIONS:
Does anyone know:
(1) When did the Afghan authorities last issue a report on an aircraft accident?
(2) In that case, how much time elapsed between the accident and the publication of the final report?
(3) Also in that case, was a preliminary report also issed, and if so, how much time elapsed between the accident and the publication of the preliminary report?
　
Yes, I know, "Past performance is no guarantee of future ...."

Picky, as noted in the other thread on the Bagram accident, the NTSB sent a team to contribute to the investigation. One hopes that they'll be able to give the local authorities the kind of assistance and advice that will allow for a report meeting high standards.

*crosses fingers*

I don't see the investigation turning up anything, nor do I feel they would come clean. National security is probably stepping in and the airlines are circling to get the CVR private, ect. There there is Boeing, then there is the military and their possible involvement.....

TeldorseriousAny good 'tin kicker' should be able to figure out from the witness marks on the wreckage just where each vehicle was on impact. Same for the trim position at impact.

How does disclosure of an accident cause compromise National Security?

Machinbird - First off you are not there to get the raw data, someone else is, secondly we can fully expect that A) someone screwed up B) they will circle the wagons to not accept and shift responsibility.

All that, I hope these pilots didn't die in vain and that we can learn from their sacrifice.

The CVR/FDR equipment rack is located on the main deck on the left hand side, just aft of the rear entry door. Probably a loose vehicle crashed into that area detaching the electrical cabling.

On 744 freighters I'm familiar with, a spare aircraft parts cabinet is located in that area, too, on the main deck.

Sounds like the fuselage was also punctured, spilling the contents of the box on the runway.

As I pointed out in the closed Rumours & News thread, you won't get a message if your FMC computes an aft CG and actual CG is very far aft ;)

The pressure switch check is a very primitive, not like a W&B System.

Hell no!! I have been missloaded and overweight many times (only finding out enroute and after landing). Twice had to divert for fuel, once unexpected rotation probably 15kts prior to rotation speed, just about on V1. We were severely misloaded. None the less the W/B would be caught in FMS trend data on the previous flight and would not have an effect large enough to catch on the first flight, severely disruptive. Hell the life of a freight dog, check your cargo.

To add to NSEU post #34 comments.
You can see likely evidence of a hull rupture on the following frame grab from the video. Yes, it is very coarse, but the two dark blobs (possibly a 3rd forward of that) visible on the after part of the fuselage outline don't belong there. I would not call the photo conclusive proof, just a strong indicator.

http://home.comcast.net/~shademaker/52-1pp.jpg

Well, the white halo around the wings and fuselage doesn't belong there either. (Unless they encountered St. Elmo's Fire.)

Digital JPEG and video compression and sharpening can cause all kinds of shapes and artifacts to be added to an image.

Heck, there is a "notch" in the lower fuselage just ahead of the wings - is that "likely evidence" that the hull was cracked and the cockpit was about to fall off? There's another "notch" on the top of the fuselage just ahead of the Vstab. Maybe an MRAP went out the ceiling? (Sarcasm alert!)

I'm just saying, as a professional image editor (among other things) that there are no blobs (digital imaging artifacts) on the aft lower fuselage that aren't replicated all over this image. And they are indicators of precisely - nothing.

Why would a jet fly 1 hour in the wrong direction, to pick up fuel, when such a small quantity was available at bastion? DXB/OMDW is only 2 1/2 hours away, so why fly in completely the wrong direction for an hour, extend your next leg by an hour, when fuel is already available at OAZI? What makes no sense is they would have reduced their MTOW by flying up to OAIX, 5000 feet up, with significant terrain issues and required climb gradients, when topping up at OAZI would have made far more sense with far less gradient requirements.

I am guessing they dropped or picked up at Bagram, why they are claiming they didnt is anyones guess.

Clearly, you have never operated for the USAF. Nothing about that routing is grounds for conspiracy.

GF