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AGL versus MSL Project

 

What is the “AGL Versus MSL Project?”

After a considerable amount of work on the “Victor Airways Project” I began thinking about how much free-fall time (expressed as altitude) Cooper might have had, or, more importantly, might have thought he had.

 

I also wondered if the altitude he specified was an ideal altitude, a good altitude, or maybe a very poor altitude. To answer this question I went to the D. B. Cooper thread on Dropzone.com [HERE] and asked this question [HERE’S THE QUESTION].

 

I got a response that was intriguing from a skydiver named Orange1. Look at [THIS ANSWER].

 

Now, this really did get me to thinking.

 

As a pilot, I know that pilots almost always fly (and think) of altitudes being expressed in Mean Sea Level (MSL) as opposed to Above Ground Level (AGL). The exception being when landing, and it that case they have Traffic Pattern Altitudes published in MSL to ensure they are at the appropriate AGL altitude (but the read them as MSL). For example: If the standard altitude for landing traffic, called Traffic Pattern Altitude (TPA), at an airport is 8oo ft. AGL and the runway elevation is 400 ft. MSL the TPA will show on the charts as 1200 ft. MSL.

 

According to Orange1, skydivers almost always jump and think in altitudes being expressed in AGL. For example if a skydiver wants to free-fall 6,000 ft. and wants a 6,000 ft. buffer for safety they would express the desired altitude as 12,000 ft. (AGL). If the dropzone (DZ) was at 1,200 ft altitude the pilot would fly over the DZ at 13,200 ft. MSL.

 

When Dan Cooper specified an altitude to for the pilots of Flight 305 to fly, he specified 10.000 ft. and did not designate whether he meant AGL of MSL. The pilots, of course, flew at 10,000 ft. MSL. So why is the worth discussing? Here is why:

 

The plane could have flown over terrain as high as 6,097 ft MSL (at one location). If Cooper was planning for a 4,000 ft. free-fall, he would have splattered at this location. (Remember, it was dark with heavy cloud cover.) Other locations present similar situations. Since I have no idea how long Cooper wanted to free-fall I can only use this as an example.

 

A detailed knowledge of the topography in a very large area (much more detailed than afforded by an aviation chart) would have been required to ensure Cooper’s success if he had no idea where he was.

 

There are other issues that make this worth discussing, but I’m not going to state them (at this time) because it my prejudice the thinking of others, and I prefer to hear their thoughts without that prejudice.

 

If this material leads you to any conclusions about whether or not Cooper was a skydiver, a pilot, neither, a meticulous planner, or was just winging it, please e-mail your thoughts to me at Sluggo@N467US.com

 

I have created some profiles of all the Victor Airways that were available to route an aircraft south (toward Mexico or Reno) in 1971. They are all JPEGs.

 

You may download them below. [Please don’t link to these files]

 

 

Files for Download

 

 

Victor 4 and Victor 25

V-4 and V-25 Elev Profile.jpg

A profile image of Victor 4 and Victor 25 150 miles out from SEA. Note: the vertical scale is 6,500 ft. MSL.

[Click Here]   {264 KBytes}

V-4 and V-25 Map for Elev Profile.jpg

A map image of Victor 4 and Victor 25 150 miles out from SEA.

[Click Here]   {981 KBytes}

 

 

 

Victor 4, 21 and 23

V-4, V-21 and V-23 Elev Profile.jpg

A profile image of Victor 4, Victor 21and Victor 23 to 150 miles out from SEA. Note: the vertical scale is 6,500 ft. MSL.

[Click Here]   {266 KBytes}

V-4, V-21 and V-23 Map for Elev Profile.jpg

A map image of Victor 4, Victor 21and Victor 23 to 150 miles out from SEA.

[Click Here]   {2,437 KBytes}

 

Victor 23

V-23 Elev Profile 150 Miles.jpg

A profile image of Victor 23 to 150 miles out from SEA. Note: the vertical scale is 4,500 ft. MSL.

 

[Click Here]   {251 KBytes}

V-23 Map for Elev Profile 150 Miles.jpg

A map image of Victor 23 to 150 miles out from SEA.

[Click Here]   {885 KBytes}

 

Victor 27

V-27 Elev Profile 150 miles.jpg

A profile image of Victor 27 to 150 miles out from SEA. Note: the vertical scale is 4,500 ft. MSL.

[Click Here]   {253 KBytes}

V-27 Map for Elev Profile 150 miles.jpg

A map image of Victor 27 to 150 miles out from SEA.

[Click Here]   {1,359 KBytes}

Victor 165-A

V-165A Elev Profile.jpg

 

A profile image of Victor 165-A to 150 miles out from SEA. Note: the vertical scale is 4,500 ft. MSL.

[Click Here]   {302 KBytes}

V-165A Map for Elev Profile.jpg

A map image of Victor 165-A to 150 miles out from SEA.

[Click Here]  {776 KBytes}

Victor 165-B

 

V-165B Elev Profile.jpg

A profile image of Victor 165-B to 150 miles out from SEA. Note: the vertical scale is 4,500 ft. MSL.

 

[Click Here]   {257 KBytes}

V-165B Map for Elev Profile.jpg

A map image of Victor 165-B to 150 miles out from SEA.

[Click Here]   {723 KBytes}

 

Victor 287

 

V-287 Elev Profile.jpg

A profile image of Victor 287 to 136 miles out from SEA. Note: the vertical scale is 4,500 ft. MSL and this profile only goes out 136 miles to the BTG VORTAC (where V-23 would be followed thereafter).

 

[Click Here]   {288 KBytes}

V-287 Map For Elev Profile.jpg

A map image of Victor 287 to 136 miles out from SEA. Note: this Victor Airway only goes out 136 miles to the BTG VORTAC (where V-23 would be followed thereafter).

[Click Here]   {663 KBytes}

 

Actual Flt 305 Flight Path

 

Actual 305 Flight Path Elev Profile.jpg

A profile image of the Actual 305 Flight Path. Note: the vertical scale is 4,500 ft. MSL and this profile only goes out 140 miles.

 

[Click Here]   {313 KBytes}

Actual 305 Flight Path Map of Elev Profile.jpg

A map image of the Actual 305 Flight Path.

[Click Here]   {707 KBytes}

 

 

 

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This page was last revised: March 13, 2009.