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#1
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"David Brooks" writes:
Is there any problem with controllers or examiners if I cross a stepdown fix several hundred feet above the depicted altitude? I believe that, legally, I can be at any altitude above the crossing minimum, but would this be a bust of the PTS +/-100 tolerance, or cause a problem for ATC? There's an interesting article from a 1998 Transport Canada newsletter called "CFIT - Why are aircraft flying at minimum IFR altitudes?": http://www.tc.gc.ca/civilaviation/an...rna/new198.htm One of the major recommendations is that the only time a pilot should fly at (rather than above) a minimum IFR altitude is MDA when weather conditions require; otherwise, leave a healthy safety margin. Of course, you'll have a hard time convincing a flight test examiner of this, but in real life, it makes sense to me -- my plane is a lot slower and can descend at a lot steeper angle than a big airliner, so I don't need a long, shallow approach slope anyway. Besides, ATC doesn't always know what approach you're flying anyway. Are you on the ILS 25, the LOC 25, the LOC/DME 25, the NDB 25, the NDB/DME 25, or the GPS 25? In my (so-far limited) experience, sometimes they mention a specific approach and sometimes they do not. All the best, David |
#2
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In a previous article, David Megginson said:
One of the major recommendations is that the only time a pilot should fly at (rather than above) a minimum IFR altitude is MDA when weather conditions require; otherwise, leave a healthy safety margin. Of course, you'll have a hard time convincing a flight test examiner of this, but in real life, it makes sense to me -- my plane is a lot slower and can descend at a lot steeper angle than a big airliner, so I don't need a long, shallow approach slope anyway. I don't know if this would be considered "a healthy safety margin", but my examiner said the same thing that my instructor did - that the PTS says +100 feet/-0 feet, so you should always fly 50 feet high to give yourself a bit of a buffer. -- Paul Tomblin http://xcski.com/blogs/pt/ Pascal - A programming language named after a man who would turn over in his grave if he knew about it. |
#3
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#4
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Why would you want to add extra work? The approaches are published that way
for a reason. Also, another poster commented about staying at an altitude (above the published one) until intersecting the 'GP.' I can only assume "GP" means glide path (or glide slope). Your example was a VOR appch I believe, but in the case of an ILS approach, it is not wise to stay above, as you can intercept a false glideslope. If you do the approach your way then you have to account for wind, etc to figure out if you are at the right descent speed, etc. Just descend as published - it is easier than figuring out a descent rate to match the winds and airplane speed. The bottom line is the approach is the approach - I don't think it is intended as a "suggestion." - why stay above the heights? Wouldn't you rather get down as fast as possible than be in the clouds? The altitudes on the approach chart guarantee more than reasonable obstacle clearance - not performing the approach as published would also lead me to wonder if there are other things you would make up your own procedures for and as a DE I would consider that a bad thing... tim "David Brooks" wrote in message ... Is there any problem with controllers or examiners if I cross a stepdown fix several hundred feet above the depicted altitude? I believe that, legally, I can be at any altitude above the crossing minimum, but would this be a bust of the PTS +/-100 tolerance, or cause a problem for ATC? For example, take the SEA VOR 34L/R approach. Assume you are cleared for the approach at 5000ft. Profile is 5000 at FACTS - 6nm - 3000 at MILLT - 6.7nm - 1600 at DONDO, which is the last fix before descent to the MDA. I can set up a nice smooth descent at 300fpnm, arrive at 1600ft well before DONDO, and avoid even thinking about a level-off by crossing MILLT something above 3200ft. Would that be a checkride ding? -- David Brooks |
#5
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For the VOR approaches, you probably want to get down more or less on the
steps. You'll need the time to find the airport if you do break out in many cases. You don't however have to execute the approach as steps unless the altitudes are depicted as mandatory altitudes (line above and below the number). If it is a long approach, there is no need to go bombing down to the next altitude as you cross each stepdown. Bby the same token you don't want to be too far above the min crossing altitude when you cross it, otherwise you're not going to have enough room to get down with a reasonable descent rate. Ideally, you would decend at a rate that got you to the min crossing altitude as you passed the next stepdown fix, but that usually won't happen. Now on an ILS, you should be following the glideslope if it is working. The stepdowns there are for a localizer only approach. Note that staying high on the ILS until intercepting the GS will never put you in a position to get a false GS: You'll still intersect the glideslope from underneath. Tim J wrote: tim "David Brooks" wrote in message ... Is there any problem with controllers or examiners if I cross a stepdown fix several hundred feet above the depicted altitude? I believe that, legally, I can be at any altitude above the crossing minimum, but would this be a bust of the PTS +/-100 tolerance, or cause a problem for ATC? For example, take the SEA VOR 34L/R approach. Assume you are cleared for the approach at 5000ft. Profile is 5000 at FACTS - 6nm - 3000 at MILLT - 6.7nm - 1600 at DONDO, which is the last fix before descent to the MDA. I can set up a nice smooth descent at 300fpnm, arrive at 1600ft well before DONDO, and avoid even thinking about a level-off by crossing MILLT something above 3200ft. Would that be a checkride ding? -- David Brooks -- --Ray Andraka, P.E. President, the Andraka Consulting Group, Inc. 401/884-7930 Fax 401/884-7950 http://www.andraka.com "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 |
#6
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On Sat, 18 Oct 2003 01:36:18 GMT, "Tim J"
wrote: Also, another poster commented about staying at an altitude (above the published one) until intersecting the 'GP.' I can only assume "GP" means glide path (or glide slope). Your example was a VOR appch I believe, but in the case of an ILS approach, it is not wise to stay above, as you can intercept a false glideslope. Well of course you don't want to intercept a GP from above, but that has nothing to do with remaining above the published GP intercept altitude miles from the FAF where the GP will be above you. For example, look at the ILS 14 at Nashua, NH (KASH). The GP intercept altitude is 1800' and the precision FAF is about five miles from the runway. It would not be unusual to be vectored to the vicinity of MUGGY at an altitude of 3000' (or even 2500' if memory serves me) and then cleared for the approach. At that point in space, you are well below the GP (so no danger of intercepting a false glideslope). I would prefer to remain straight and level until intercepting the GP, and then just do the one reconfiguration to a descent. The alternative is more work as you configure for a descent, level off at 1800' and reconfigure for straight and level, and then reconfigure again for a descent just outside of CHERN. Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA) |
#7
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Tim J wrote: The bottom line is the approach is the approach - I don't think it is intended as a "suggestion." - why stay above the heights? Wouldn't you rather get down as fast as possible than be in the clouds? The altitudes on the approach chart guarantee more than reasonable obstacle clearance - not performing the approach as published would also lead me to wonder if there are other things you would make up your own procedures for and as a DE I would consider that a bad thing... Another "bottom line" is that the stepdown altitude in a NPA profile is a *minimum* altitude. If you think in terms of getting down to a stepdown to "get out of the clouds" that is a good way to find granite or trees instead of water vapor. This is not just my view; the industry/government accident stats are replete. |
#8
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wrote in message ... If you think in terms of getting down to a stepdown to "get out of the clouds" that is a good way to find granite or trees instead of water vapor. This is not just my view; the industry/government accident stats are replete. Only if the published altitudes are wrong. |
#9
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"Steven P. McNicoll" wrote: wrote in message ... If you think in terms of getting down to a stepdown to "get out of the clouds" that is a good way to find granite or trees instead of water vapor. This is not just my view; the industry/government accident stats are replete. Only if the published altitudes are wrong. I guess the stats and industry/government studies are all wet then. The published altitudes weren't wrong at KBDL when the AAL MD80 hit the trees near the stepdown fix. |
#10
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So what are you saying? The approach chart is/was wrong or the pilots made
an error? wrote in message ... "Steven P. McNicoll" wrote: wrote in message ... If you think in terms of getting down to a stepdown to "get out of the clouds" that is a good way to find granite or trees instead of water vapor. This is not just my view; the industry/government accident stats are replete. Only if the published altitudes are wrong. I guess the stats and industry/government studies are all wet then. The published altitudes weren't wrong at KBDL when the AAL MD80 hit the trees near the stepdown fix. |
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