The photo below shows an interesting wreckage piece.
I have put on line the photo above on this web site, writing that it was characteristic and that any person having seen it during manufacturing or maintenance should be able to recognize it. I was surprised to have found nowhere somebody arguing that the presence of this piece of wreckage on the pentagon's lawn proved the presence or the particular type of plane which contains it.
Shortly after having put on line the picture with this comment, I received the following email from Mike Waltz <firstname.lastname@example.org>
I saw this pic on your site. I recognize the cylindrical part mounted on the plate at the lower middle of the picture. It is definitely part of a 757. It is a geared rotary actuator for the slats, made by Sundstrand. I worked on this unit over about 2 years, doing manufacturing support and some small design changes. The end cover and housing are missing, but I recognize the mounting flange (which has a very distinctive shape), input shaft, ring gears, and I can see one of the planet gears. Definitely a 757 slat actuator.
Asking some precisions, I got the answer :
The slats are flaps on the leading edge of the wing. There are ~12
actuators on each wing, which drive the slats forward and backwards on
tracks. They are all driven by a series of drive shafts which span the
wing. The shafts are driven by a hydraulic PDU (power drive unit) which is
in the belly of the aircraft.
Here is the manufacturer's page for the actuator. The picture on that page is an old model. The new model of the actuator has a slightly more rounded shape, and is painted with a green primer instead of white paint. Also note that it's listed for 757 only.
I am trying to find a schematic of the entire slat system, but I can't find it yet. Our company designed only the actuator, not the whole system, so I think Boeing would have the schematics showing all the parts of the system.
This information is important. If the affirmation of Mike Waltz is confirmed, if this actuator is used on B 757 only, it could be considered to be a proof of the crash on this plane on the pentagon, but ONLY IF there is something strong and not subject to doubt wether this photo was shot on the lawn of the pentagon on septembre 11. The part could have been taken from another 757 crash site and the photo shot in any place or even later on the pentagon's lawn...