JHSfan
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Massive Test Probe On 741

Fri Sep 29, 2006 2:44 am

On h.. of a massive probe - Why?

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I suppose that Boeing wanted data from a point forward of the plane, a point where the air is still relatively "untouched" by the flying plane.
Someone must have an idea of why, thanks.

Yours in realtime
JHSFan
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KELPkid
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 3:24 am

When the pitot tube probe is placed far ahead of the aircraft, it is much less prone to installation error (and, as a matter of fact, helps the engineers determine what the installation error is on the final placement of the pitot tube  Wink ). Also, many flight test articles contain Angle-of-Attack instrumentation in the long test boom (extremely useful data for flight testing!).
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avioniker
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 3:54 am

The "massive" probe size was to diffuse the aerodynamic stress placed on the nose by such a long probe. Much like the Eiffel tower having a wider base than tip.
 Smile
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Starlionblue
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 5:27 am

Well, the particular 747 had just seen a very cute 727 passing on the taxiway and couldn't control himself at this early hour...
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jamesbuk
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 5:38 am

"I'm a real plane!!". " whys my nose growing, i am real i am!"

but seriously im guessing that it has test equipment in it, maybe to test pressures and stuff before it hits the plane.

Rgds --James--
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777wt
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 6:54 am

It's an flying dart!  Wink

Notice the tech dragging his toolbox on wheels?
 
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Starlionblue
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 8:33 am

Quoting 777WT (Reply 5):
Notice the tech dragging his toolbox on wheels?

Early roll-aboard! Big grin
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JHSfan
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 6:56 pm

Quoting Avioniker (Reply 2):
The "massive" probe size was to diffuse the aerodynamic stress placed on the nose by such a long probe. Much like the Eiffel tower having a wider base than tip

You are probably right about that, but it's not an absolute necessity.

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These two former enemy-planes shows that a tube pointing forward does not need to have a very thick connection to the fuselage.

If you take a look just below the headlight on the nose of the Nimrod, you will see a smaller version of the 741 probe. The shape is conical as the the bigger Boeing, yet size is different.

This Boeing plane has the same type of test probe:

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Boeing or maybe NASA must have fancied that shape for tests. Right now i'm looking for more info on the net about the USAF/NASA plane.

Quoting KELPkid (Reply 1):

It sound like you are making a point, thanks KELPkid.

One final note (so far) to those of you who make fun of the poor plane. Everyone thinks that it's a Pan Am plane just because it seems that way - blue and white with a visible letter "P" just like the Pan Am plane in the middle.
Naturally Pan Am would not like to have their name om such a weird looking plane. So I thinks that Boeing must have painted Pinocchio on the fuselage instead. Big grin

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JHSfan
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oly720man
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 8:35 pm

Quoting JHSfan (Reply 7):
Right now i'm looking for more info on the net about the USAF/NASA plane.

It was used in the early 1980's for winglet research. In the db there is a side view of the aircraft on the same day and the remark mentions it having winglets on. The nose probe was presumably to get accurate attitude information to correlate the winglet results.

This is a review of the tests..... It's huge >30Mb, 192 pages.

http://ntrs.nasa.gov/archive/nasa/ca...asa.gov/19840019618_1984019618.pdf



The probe will be conical for structural rigidity so the pitch and yaw probe angles measured at the tip can be relied upon. It doesn't really matter if refuelling probes bounce around a bit.


edit : added photo - go to NASA dryden multimedia to see others

[Edited 2006-09-29 13:39:07]
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avioniker
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 9:45 pm

The taper shape also allowes the boom to flow into the radome attach points used to secure the structure to the nose. The refuelling booms are attached to fuselage hard points so don't need the taper.
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One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
474218
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RE: Massive Test Probe On 741

Fri Sep 29, 2006 11:12 pm

Quoting JHSfan (Thread starter):
I suppose that Boeing wanted data from a point forward of the plane, a point where the air is still relatively "untouched" by the flying plane.
Someone must have an idea of why, thanks.

JHSfan, Your are correct, the probe is called a "Gust Boom" it allows turbulence to be measured without interference from the airframe.
 
JHSfan
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RE: Massive Test Probe On 741

Sat Sep 30, 2006 10:38 pm

Thanks a lot for your explanations.  Smile

It seems that gust booms has been replaced by a radar based wind-gust system.

- JHSfan
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kc135topboom
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RE: Massive Test Probe On 741

Sun Oct 01, 2006 7:23 pm

The boom gathers very accurate TAS (true airspeed) information. A second method to get accurate TAS is to trail a small drogue off the tip of the vertical stabilzer. But, the boom can be used to get additional information, as already has been mentioned.

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