Tower!3D Pro - Anatomy of a Landing

[crbascott]

In response to some comments and concerns about how planes behave ("slowing to a crawl") after a landing, I thought I'd take a deeper dive and look at the plane speeds at various points in the landing process. I used KSAN for my observation and had all planes exit at taxiway B10.

(1) Touch down - this is the point where I heard the tires hit the runway. All planes hit the same spot, but, obviously, at different speeds. In my test, the DH4 was traveling at approximately 80 knots, the E70 at 108 knots, 73W at 118 knots, and 753 at 112 knots.
(2) Successful landing - this was enlightening to me as all planes received the successful landing message when their speed had slowed to 45 knots. This occurred at different points based on the plane type and landing speed.
(3) Runway cruising - planes would maintain 45-48 knots until it was time to slow down to taxiing speed (19 knots) in preparation to exit the runway. All planes began slowing to taxi speed at the same point on the runway.
(4) Taxi speed - all planes reached 19 knots at the same point in the runway and would maintain this until approaching the exit taxiway.
(5) Slow down to exit and stop - all planes would then begin slowing down at the same point, exit, and come to a stop in preparation of taxiing to the ramp. 

The attached image demonstrates the above graphically.  For other exit taxiways the same pattern is followed, points 3-5 just occur sooner.

Is 45 knots an accurate "cruising" speed? What about slowing to 19 knots? I have no idea! I'm not an expert, so I just thought I'd provide this information and let more knowledgeable folks discuss further if so desired. Discuss away!

[VenturaGuy101]

I have not had time to do some testing to figure out under what circumstance I was seeing the slow taxi on the runway.  My question under your test, was the Taxi Speed (4) line determined by the distance of the exit and stop(5) or is it the previous taxiway.  In your testing the slowing to taxi speed occurs right at taxiway B9 which is the previous taxiway to the exit at B10.  This is fine at an airport and taxiways you tested at KSAN but if the exit taxiway at KBOS on 4L is N1 which makes the previous taxiway, Q.  This would be a long distance to cover at 19 knots.  If its distance and just happens to occurs at the same location as the previous taxiway at KSAN then I need to do further research to see if I can replicate the original issue that I saw.

[crbascott]

Good point, I assumed distance was the determining factor. To verify, I tested your scenario at KBOS - landing on 4L exiting at N1. Attached are three screenshots showing points 2, 3 , and 4 for an E70. I also observed a CNA and E90 and their successful landing spots were different (the CNA's was between E & C), but both "cruised" at 45-48 until the same point in the runway as the E70. So, it does appear to be distance rather than taxiway based.

  

[VenturaGuy101]

Thanks Craig for that test.  It looks like the point where an aircraft slows to taxi speed is not tied to the upstream taxiway location but it is tied to distance from the exit taxiway.  Though it seems like there is still quite a bit of distance to cover at taxi speed before it reaches taxiway N1.  So I am not sure what I saw and since I have not been able to replicate it, I must have thought I saw something that I did not.  I wish there was an expedite taxi that it would keep higher speeds runt until exit taxiway.  Well maybe that can be added for the next version of Tower!3Dx Pro. 

[N737NW]

A quick question... perhaps it was answered earlier in this thread, but I'm too dense to detect it.  :)

Does the exit-to-taxi speed of 19 kts vary at all for the high speed taxiways, such as those at KLAX or KLAS?  In other words, can a plane take an earlier high-speed taxiway at a higher speed or will they meander down the runway until reaching 19 kts?

[crbascott]

2 hours ago, N737NW said:

A quick question... perhaps it was answered earlier in this thread, but I'm too dense to detect it.  :)

Does the exit-to-taxi speed of 19 kts vary at all for the high speed taxiways, such as those at KLAX or KLAS?  In other words, can a plane take an earlier high-speed taxiway at a higher speed or will they meander down the runway until reaching 19 kts?

No it wasn't answered.

A plane will not take an earlier exit than it physically can - i.e., it will not exit until it has slowed to 45 knots. In the example above, the following is the earliest exit these planes would take: DH4-B5, E70-B6, 73W-B7, 753-B8.

So to directly answer your questions, planes do not have to slow down to 19 knots to exit.

DISCLAIMER: The landing distances above were done back in November. With SPs for both Tower and RT, results now could be slightly different.

[N737NW]

thanks for the clarification, much appreciated!

[crbascott]

You're welcome, but I'd really appreciate it if you wouldn't stick your tongue out at me! ;)