737NG vs. C-40A Clipper air data probe question

[Lone Star One]

Greetings everyone, this is my first post here, but in searching for an answer I was pointed this way as one of two forums by some pilot friends.

I am working on some aviation prints of various commercial and military aircraft and currently have been working on some prints of 737-700 series aircraft. One of them will be of VR-59's C-40A Clippers (based at NAS Fort Worth JRB/Carswell Field). In my research on the various external details of the 737-700 for my artwork, I've come across what looks like two different air data probe systems (I think that's the right terminology....), one of the civilian 737-700s and one which appears unique to the C-40As.

Here are some links to Airliners.net pics to illustrate:
http://www.airliners.net/open.file/0599788/L/
http://www.airliners.net/open.file/0623403/L/
The above two shots are of a 737-600, but I think it should be the same across the NG family.
http://www.airliners.net/open.file/1038025/L/
The above single link is to the left side of a C-40A Clipper.

Differences I noted:

1. The Clipper has two pitot probes on the left side whereas the other has only one and its placed further forward.

2. There is a small hatch under the cockpit window on the right side of the civilian NGs but on the Clipper that small hatch/panel is on both sides under the cockpit.

3. I believe it's the AoA vane that is under the pitot probe on the left side of the civilian NG but on the Clipper it is between the two pitot probes.

I try and make my illustrations as accurate as possible and a lot of times I have to ask questions that don't necessarily affect what I end up doing, but I like to at least understand the differences for future projects I have planned.
So my question is this:

Do C-40A Clippers have a different air data system than civilian NGs and if so, is it due to some sort of increased redundancy that the Navy requires?
Thanks to everyone in advance!

[j_davey]

i dont have any answer for you but just something to add: the arrangement on the C-40A seems to be the same as the Classic 737`s (3/4/5), which incidentally make it really difficult to dock an airbridge but thats another topic altogether.

http://www.airliners.net/open.file/1177307/M/
jd.

[CaptainSandL]

What very keen eyes you have got!

1. The Clipper has two pitot probes on the left side whereas the other has only one and its placed further forward.

Yes, this is the same arrangement as the 737 Classics.

2. There is a small hatch under the cockpit window on the right side of the civilian NGs but on the Clipper that small hatch/panel is on both sides under the cockpit.

This is the cover of an external handle to open the Capts DV window from the outside. It was a standard fit to have this on both sides for the 737-200C but I have not noticed it on the Classic or NG before.

3. I believe it's the AoA vane that is under the pitot probe on the left side of the civilian NG but on the Clipper it is between the two pitot probes.

It is the same arrangement as the Classics. Why, I don't know!

S&L

[IRRenewal]

2. There is a small hatch under the cockpit window on the right side of the civilian NGs but on the Clipper that small hatch/panel is on both sides under the cockpit.Commonly found on P1 side of 737s converted to freighters. Something to do with getting out in case the cargo shifts. That C-40A in the picture has a cargo door, which probably explains why.

Edited to add: after bit of searching on airliners.net, I found the following picture (http://www.airliners.net/open.file?id=0957784&size=L&width=1280&height=865&sok=JURER%20%20%28ZNGPU%20%28nvepensg%2Cnveyvar%2Ccynpr%2Ccu bgb_qngr%2Cpbhagel%2Cerznex%2Ccubgbtencure%2Crznvy%2Clrne%2C ert%2Cnvepensg_trarevp%2Cpa%2Cpbqr%29%20NTNVAFG%20%28%27%2B% 22punaary%22%20%2B%22rkcerff%22%20%2B%22DP%22%27%20VA%20OBBY RNA%20ZBQR%29%29%20%20beqre%20ol%20cubgb_vq%20QRFP&photo_nr=33&prev_id=0965407&next_id=0952545) of a Channex QC which also shows the small hatch under the P.1 no 2 window.

Gerard

[Lone Star One]

Thank you all for your responses, this has been very helpful in my artwork!

The main reason was the addition of the cargo door, which you will notice is where the static ports are located on a standard NG.
In reference to your question, I take it then that the static ports are that baremetal oval-shaped area underneath the third passenger window?

If I might take this a bit further:

What is the function, then of the round baremetal port lower and a bit aft of the static ports (it's roughly under the fourth pax window)?

There is also a small pitot-appearing item on the lower sides of the nose roughly in line with the nose landing gear leg- what purpose does that serve?

Again, this doesn't affect my final artwork, but I have a bit of an obsessive habit of wanting to understand what it is I'm drawing!

[IRRenewal]

There is also a small pitot-appearing item on the lower sides of the nose roughly in line with the nose landing gear leg- what purpose does that serve?If you mean the probe just in front of the 'sunseekers' logo, that's the TAT probe (Total Air Temperature).
Gerard

[CaptainSandL]

More info on the probes here (http://www.b737.org.uk/probes.htm).

[Golden Rivet]

Pitot-static probes are fitted to the classic 737, whereas Pitot probes are fitted to the NG.