why DME??

I_WANNA_BE_ATP · October 12th, 2004, 10:07

Can anyone tell me why the FAA makes DME a requirement for flight s above 24,000 feet?

Also, does anyone actually ever use VFR on top???

Just some questions that popped into my mind during my instrument ground. The instructor wasn't sure why DME is needed. His best thought was if you are not in radar coverage and ATC wants to know your location. He also said VFR on top is useless. I tend to agree.

mtsu_av8er · October 12th, 2004, 10:33

[ QUOTE ]
He also said VFR on top is useless. I tend to agree.

[/ QUOTE ]

And if there's ice in the clouds and you're in a C172? Seems pretty worthwhile then....

roundout · October 12th, 2004, 12:39

[ QUOTE ]
The instructor wasn't sure why DME is needed. His best thought was if you are not in radar coverage and ATC wants to know your location. He also said VFR on top is useless. I tend to agree.

[/ QUOTE ]

good instructor

av8rmsu · October 12th, 2004, 20:02

[ QUOTE ]
[ QUOTE ]
The instructor wasn't sure why DME is needed. His best thought was if you are not in radar coverage and ATC wants to know your location. He also said VFR on top is useless. I tend to agree.

[/ QUOTE ]

good instructor

[/ QUOTE ]

That's a pretty harsh comment. Why would 99% of instructors who don't fly in the flight levels know the answer to this question?

The only thing I can think of is for navigation purposes. DME is good for 199nm from the station (supposedly). But what if I am over the Atlantic at FL360...not much good there?

VFR-on-top is not useless. I have used it before. ATC tried to route me all over the place in Texas. I was VMC (on top of a layer) and wanted to go direct. Told them I wanted to cancel IFR..."squawk VFR, frequency change approved, have a good flight".

roundout · October 12th, 2004, 20:29

actually, you're right. i didn't mean to get the part about DME in there, just the VFR-on-top. VFR-on-top isn't useless.

btw, if you cancelled IFR, that doesn't qualify as VFR-on-top, it qualifies as VFR. if yu're VFR-on-top, you're still on an IFR flight plan and you're still in touch with ATC squawking an IFR code. there's a big difference between VFR-on-top and getting a clearance to pop above some clouds and then cancelling.

av8rmsu · October 12th, 2004, 22:23

very true....

i hope you did catch my point...

i didn't think that through very well

roundout · October 12th, 2004, 22:25

not really....what was your point?

av8rmsu · October 12th, 2004, 22:38

1. VFR-on-top is not useless (we both agree)

2. Don't criticize instructors for not knowing answers that have nothing to do with there particular type of flying.

roundout · October 12th, 2004, 22:47

[ QUOTE ]
i didn't mean to get the part about DME in there

[/ QUOTE ]

I_WANNA_BE_ATP · October 13th, 2004, 11:17

Actually, my instructor used to work for a major airline and is now retired with thousands of hours. I guess I should have included that he suggested that you should fly in the IFR system as much as possible.

PhilosopherPilot · October 15th, 2004, 17:55

[ QUOTE ]
1. VFR-on-top is not useless (we both agree)

2. Don't criticize instructors for not knowing answers that have nothing to do with there particular type of flying.

[/ QUOTE ]

You shouldn't criticize an instructor for not knowing an answer, but you should criticize them for pretending to know something, or just blabbing about something they don't know about.

Instead, an instructor should say, "I don't know the answer to that. Let me do some research and get back to you."

My .02....

G

Ophir · October 20th, 2004, 11:30

A great use of VFR on top is when you are wanting to cruise below the MEA on a route that is extremely high, like for example the V484 out of SLC to BOI has a MEA of 16000 but you don't need that for terrain clearance, only reception. So you request VFR on top and cruise at 11,500 and stay below the require O2 altitude.

An additional place where it makes a tremendous amount of sense is coming into a busy airport and starting your descent when you want to rather than when you are told to. When arriving into SLC on a VFR on top clearance you can put in a VNAV profile that will get you out of high altitude (again 02 requirement), increase your forward groundspeed, and make your routing and handling much easier than arriving via a STAR.

In truth the VFR on top clearance is really helpful so long as you know how to use it. Use it as though you don't really want to cancel your IFR clearance but you want to provide your own terrain clearance (and traffic of course).

October 12th, 2004, 10:07	#1
I_WANNA_BE_ATP Senior Member Join Date: Jul 2004 Location: 3rd Rock From the Sun Posts: 860	why DME?? Can anyone tell me why the FAA makes DME a requirement for flight s above 24,000 feet? Also, does anyone actually ever use VFR on top??? Just some questions that popped into my mind during my instrument ground. The instructor wasn't sure why DME is needed. His best thought was if you are not in radar coverage and ATC wants to know your location. He also said VFR on top is useless. I tend to agree.

October 12th, 2004, 10:33	#2
mtsu_av8er Old Skool Join Date: Dec 2002 Location: Utopia Posts: 12,477	Re: why DME?? [ QUOTE ] He also said VFR on top is useless. I tend to agree. [/ QUOTE ] And if there's ice in the clouds and you're in a C172? Seems pretty worthwhile then....

October 12th, 2004, 12:39	#3
roundout Senior Member Join Date: Apr 2004 Location: kads Posts: 805	Re: why DME?? [ QUOTE ] The instructor wasn't sure why DME is needed. His best thought was if you are not in radar coverage and ATC wants to know your location. He also said VFR on top is useless. I tend to agree. [/ QUOTE ] good instructor

October 12th, 2004, 20:02	#4
av8rmsu Senior Member Join Date: Aug 2003 Location: Pickwick Lake Posts: 448	Re: why DME?? [ QUOTE ] [ QUOTE ] The instructor wasn't sure why DME is needed. His best thought was if you are not in radar coverage and ATC wants to know your location. He also said VFR on top is useless. I tend to agree. [/ QUOTE ] good instructor [/ QUOTE ] That's a pretty harsh comment. Why would 99% of instructors who don't fly in the flight levels know the answer to this question? The only thing I can think of is for navigation purposes. DME is good for 199nm from the station (supposedly). But what if I am over the Atlantic at FL360...not much good there? VFR-on-top is not useless. I have used it before. ATC tried to route me all over the place in Texas. I was VMC (on top of a layer) and wanted to go direct. Told them I wanted to cancel IFR..."squawk VFR, frequency change approved, have a good flight".

October 12th, 2004, 20:29	#5
roundout Senior Member Join Date: Apr 2004 Location: kads Posts: 805	Re: why DME?? actually, you're right. i didn't mean to get the part about DME in there, just the VFR-on-top. VFR-on-top isn't useless. btw, if you cancelled IFR, that doesn't qualify as VFR-on-top, it qualifies as VFR. if yu're VFR-on-top, you're still on an IFR flight plan and you're still in touch with ATC squawking an IFR code. there's a big difference between VFR-on-top and getting a clearance to pop above some clouds and then cancelling.

October 12th, 2004, 22:23	#6
av8rmsu Senior Member Join Date: Aug 2003 Location: Pickwick Lake Posts: 448	Re: why DME?? very true.... i hope you did catch my point... i didn't think that through very well

October 12th, 2004, 22:25	#7
roundout Senior Member Join Date: Apr 2004 Location: kads Posts: 805	Re: why DME?? not really....what was your point?

October 12th, 2004, 22:38	#8
av8rmsu Senior Member Join Date: Aug 2003 Location: Pickwick Lake Posts: 448	Re: why DME?? 1. VFR-on-top is not useless (we both agree) 2. Don't criticize instructors for not knowing answers that have nothing to do with there particular type of flying.

October 12th, 2004, 22:47	#9
roundout Senior Member Join Date: Apr 2004 Location: kads Posts: 805	Re: why DME?? [ QUOTE ] i didn't mean to get the part about DME in there [/ QUOTE ]

October 13th, 2004, 11:17	#10
I_WANNA_BE_ATP Senior Member Join Date: Jul 2004 Location: 3rd Rock From the Sun Posts: 860	Re: why DME?? Actually, my instructor used to work for a major airline and is now retired with thousands of hours. I guess I should have included that he suggested that you should fly in the IFR system as much as possible.

October 15th, 2004, 17:55	#11
PhilosopherPilot Senior Member Join Date: Jul 2003 Location: Providence, RI Posts: 454	Re: why DME?? [ QUOTE ] 1. VFR-on-top is not useless (we both agree) 2. Don't criticize instructors for not knowing answers that have nothing to do with there particular type of flying. [/ QUOTE ] You shouldn't criticize an instructor for not knowing an answer, but you should criticize them for pretending to know something, or just blabbing about something they don't know about. Instead, an instructor should say, "I don't know the answer to that. Let me do some research and get back to you." My .02.... G

October 20th, 2004, 11:30	#12
Ophir Senior Member Join Date: Mar 2002 Location: was Ophir, CO, now in SLC! Posts: 1,477	Re: why DME?? A great use of VFR on top is when you are wanting to cruise below the MEA on a route that is extremely high, like for example the V484 out of SLC to BOI has a MEA of 16000 but you don't need that for terrain clearance, only reception. So you request VFR on top and cruise at 11,500 and stay below the require O2 altitude. An additional place where it makes a tremendous amount of sense is coming into a busy airport and starting your descent when you want to rather than when you are told to. When arriving into SLC on a VFR on top clearance you can put in a VNAV profile that will get you out of high altitude (again 02 requirement), increase your forward groundspeed, and make your routing and handling much easier than arriving via a STAR. In truth the VFR on top clearance is really helpful so long as you know how to use it. Use it as though you don't really want to cancel your IFR clearance but you want to provide your own terrain clearance (and traffic of course).

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