747 Water Tankers

[United744]

The drops are flown manually. They follow a lead aircraft that lines them up with the drop line, then it breaks off when the tanker is lined up for its run. It is the most precision piece of visual flying (with the aid of dedicated nav systems) that you'll see.

[Jeroen Hoppenbrouwers]

What kind of lead aircraft? What kind of drop air speeds?


Hoppie

https://www.youtube.com/watch?v=GjhsUoPm_QM

shows a lot. A turboprop lead, and likely flaps 20 out for the drop.

There are even shots from UNDER the drop... baaaaaaaaah!

https://www.youtube.com/watch?v=ofYaLXCpVCw

[Jeroen Hoppenbrouwers]

Loading answers partially here:

https://www.youtube.com/watch?v=0Ky5QoGh8WQ

Loading time is now down to under 13 minutes! They load both compressed air (to flush the tanks quicker during the drop) and water. The airport crash tender(s) are used as pumps. That will help  :-)


Hoppie

[Phil Bunch]

From the videos, it seemed to me that the water + air tanks occupied about half of the interior volume of the aircraft.  Since they seem to be able to handle more weight without approaching MTOW, why didn't they use bigger tanks?  Part of the answer may be that they can safely land with full fire suppression tanks if needed, saving significant money.

I wonder what combination of logistics and other considerations dictated the choice to not fill the interior with tanks.

[John H Watson]

Since they seem to be able to handle more weight without approaching MTOW

They probably took into account a failure of the water dumping system. In this case, maximum landing weight would be the limitation.

[Mark]

I wonder what combination of logistics and other considerations dictated the choice to not fill the interior with tanks.

My theory is that it's pure financial (& reuse) reasons - Global Super Tanker is just the latest in a sequence of companies (prior one went bankrupt according to wikipedia), it appears that this new company bought the equipment from the old company/aircraft and retrofitted it to the newer aircraft.

I'm all for reuse rather than scrapping.

Quote from wikipedia:

As of August 2015, Global SuperTanker Services, LLC (the successor to the defunct Evergreen Supertanker Services), has since purchased all the physical assets and intellectual property related to Evergreen's original Supertanker (except the 747-100 airframe itself) from Jet Midwest. They have transplanted the existing sprayer tank system from the 747-100 into a newer Boeing 747-400 (N744ST) airframe.[6][7][7][8]

https://en.wikipedia.org/wiki/Evergreen_747_Supertanker

[Markus Vitzethum]

Here is another video from the cockpit, taken supposedly 3 weeks ago.
https://www.youtube.com/watch?v=T6pBbIl23U8
Looks like EGPWS is "default on" and showing all red due to close proximity to terrain.   

If you'd like to recreate the flights, here are the latest ground tracks from Chile:
https://www.flightradar24.com/data/aircraft/n744st

Markus

p.s.
Brian, I really like the link to popularmechanics.com because the 3D inside model is really super-cute  as you can crawl into so many areas of the 747-400 you hardly ever see as a passenger.

[G-CIVA]

https://youtu.be/TjxJ22HXg_4

https://youtu.be/NpWOsFhovEM

[Will]

I'd love to see a photo of the dumping controls. Is the release valve smart or dumb? In orther words, is there some sort of assiatance with making sure the cargo gets dropped on target, or does the loadmaster just punch the "dump" button when things look about right? Norden bombsite, perhaps?
https://en.wikipedia.org/wiki/Norden_bombsight
Are the loading and dumping controls simply placed alongside the other 747 systems, or are the interwoven somehow? Like are there any related EICAS messages?

[Jeroen Hoppenbrouwers]

I would be very surprised to learn there are new EICAS messages. These messages are deeply integrated into the EICAS software and cannot just be added; it would be a heavyweight Boeing/avionics upgrade. Typically new stuff is added by normal switches, lamps, etc. or on a separated, integrated panel with digital displays.


Hoppie