ATCers - Vectors Q?

[SiuDude]

Now, here's your homework: If there's a Cessna doing 80ktsIASonILSfinal 6 miles out, and a B737-800 behind doing 200ktsIAS;andbothhave a 20 kt headwind, how far behind the Cessna doestheB738havetobe in order to have 3 miles spacing at the Cessna'stouchdown?

(assume the Boeing will stay at 200 kts until the 3 mile final.)

My guess is 15.

 

[Blueridge]

I would say 21 miles. With the headwind, the 172 is doing 1 mile/min and the 73 is doing 3 miles/min. In the six minutes it takes the the 172 to land the 73 has covered 18 miles. Therefore to be spaced 3 miles at touchdown, the 73 has to be 21 miles in trail.

What do I win Johnny?

 

[SiuDude]

Trick question. 737s are never vectored behind Cessnas.

 

[mattpilot]

Itisatrickquestion,indeed. Buttheanswerisatleast3miles. Hedidn'taskfortimespacing.

 

[sqwkvfr]

I would say 21 miles. With the headwind, the 172 is doing 1 mile/min and the 73 is doing 3 miles/min. In the six minutes it takes the the 172 to land the 73 has covered 18 miles. Therefore to be spaced 3 miles at touchdown, the 73 has to be 21 miles in trail.

What do I win Johnny?

Nothing.

The 738 is traveling at 3 miles/minute. The Cessna is traveling at 1 mile/minute.

It'll take the Cessna 6 minutes to land, in that time the 738 will have traveled 18NM...if it started out 15NM behind the Cessna 6NM from the runway, it'll have 3NM left to travel when the Cessna touches down.

...I think....

 

[mattpilot]

1 mile a second? man.. Must be one of those french built cessnas... the F-172s, eh?

 

[minitour]

...Now, here's your homework: If there's a Cessnadoing 80 kts IAS on ILS final 6 miles out, and a B737-800 behind doing200 kts IAS; and both have a 20 kt headwind, how far behind the Cessnadoes the B738 have to be in order to have 3 miles spacing at theCessna's touchdown?

(assume the Boeing will stay at 200 kts until the 3 mile final.)

uhhhh....

hmm..maybe I will stay on this side of the deal rather than attempt toget on your side. I sometimes f*ck up when I have to figure out adescent rate/checkpoint...I couldn't imagine doing that with 150 planeson vectors for the same approach spaced out all over theplace...incredible...

Anywho, thanks for the incredibly detailed info there. Kinda neat to see how "the dark side" works sometimes...

Thanks!

-mini

 

[minitour]

1 mile a second? man.. Must be one of those french built cessnas... the F-172s, eh?

Nah...the French built Cessnas have 6 engines and 12 seating decks...you know...bigger is better.

-mini

 

[PropsForward]

6 x 3 = 18 + 3 = 21.

 

[sqwkvfr]

6 x 3 = 18 + 3 = 21.

..and subract 6 for the Cessna's starting position...15 miles behind the Cessna.