If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
VOR approach- when to descend from the FAF
On Tue, 19 Feb 2008 05:22:18 -0800, Sam Spade
wrote: Les Izmore wrote: On Mon, 18 Feb 2008 07:24:39 -0800, Sam Spade wrote: Terence Wilson wrote: On Sat, 16 Feb 2008 19:01:14 -0800, Sam Spade wrote: Terence Wilson wrote: When flying a VOR approach in which the FAF is defined by the VOR, is it appropriate to start the descent to the MAP, or next stepdown, immediately after overflying the VOR or should I wait until I have positive course guidance for the final approach segment? I ask because it can sometimes take 1-2nm for the CDI to move, which may require a rushed descent to the MAP on some approaches. Are you a simulator only pilot? I ask, because that is a question that would be answered during instrument training. Sam, I think you asked me that question before and I answered . I'm a RW instrument student. Forgive me my lousy memory. I figured your CFI-I would have covered this by now. When the two-from indicator indicated "from," you should turn to the appropriate heading and begin descent at that time. You are effectively on-course because you are over the station where the courses are very, very small. Sort of like lines of longitude at the North Pole. Now, the question is, when you are 2 miles from the VOR and the needle still has not moved (because of bad navigation, winds, whatever),and you have descended xhundred feet, what do you do? Are you going back up? Probably not. Starting down without at least some indication that the needle is moving back towards center can very well be the beginning of the pernicious and well-known accident chain. Don't do it. That would represent issues of lack of competency to be 2 miles from the station and not have a needle moving back towards center. In fact the needle should be moving back towards center far sooner than that. Well, that is precisely the reason why it is bad advice to start down with no indication of movement of the needle. If it does indeed start moving far sooner than that, then there is minimal if any penalty for waiting. If it does not start moving sooner than that, there is good reason (issues of incompetency being one) not to have already begun the descent. So I'll say it again for emphasis. Until there is some indication that the needle is moving toward the center, indicating a return to the desired course, don't descend below the FAF altitude. (The 2 miles, incidentally, was what the poster used as a basis for his question). |
#12
|
|||
|
|||
VOR approach- when to descend from the FAF
Sam Spade wrote:
I ask, because that is a question that would be answered during instrument training. Do you think that every instrument instructor has the knowledge to provide informed opinions on subjects like these? |
#13
|
|||
|
|||
VOR approach- when to descend from the FAF
Les Ismore wrote:
Well, that is precisely the reason why it is bad advice to start down with no indication of movement of the needle. I think your advice is good and would be more easily defensible if you were being evaluated by a check airman. Very few of them are TERPS experts. |
#14
|
|||
|
|||
VOR approach- when to descend from the FAF
pstanley wrote:
You do not need pos course guidance to start descent. Such a statement needs documentation, IMO. |
#15
|
|||
|
|||
VOR approach- when to descend from the FAF
Greg Esres wrote:
Sam Spade wrote: I ask, because that is a question that would be answered during instrument training. Do you think that every instrument instructor has the knowledge to provide informed opinions on subjects like these? No, but the good ones know. |
#16
|
|||
|
|||
VOR approach- when to descend from the FAF
On Tue, 19 Feb 2008 08:07:11 -0800 (PST), Greg Esres
wrote: pstanley wrote: You do not need pos course guidance to start descent. Such a statement needs documentation, IMO. This is being treated like some kind of academic angels-on-the-head-of-a-pin question. It is not. Stuff happens. I have seen enough "competent" pilots screw up a course intercept to know that it doesn't take all that much for a pilot to end up well below the FAF altitude with no positive course guidance, if he starts his descent with none. Distractions can mount up in a hurry, and one can find himself in a situation with a high pucker factor in a hurry. Few pilots who find themselves in this situation then take the proper corrective action, in my experience. They usually "try harder" to reintercept the course while going still lower. This practially always ends up in a situation that could be disastrous in actual conditions. Advising someone new to instrument flying that it is an OK thing to start a descent with no positive course guidance is a really bad thing, in my opinion, and I base that opinion on watching a lot of pilots, many of them experienced and instrument rated, screw approaches up pretty badly, for any number of reasons. I don't care what the "book" says. |
#17
|
|||
|
|||
VOR approach- when to descend from the FAF
Les Izmore wrote:
This is being treated like some kind of academic angels-on-the-head- of-a-pin question. It is not. Not to you, maybe. People ask questions here for a variety of reasons: 1) legality, 2) safety, 3) passing checkrides, 4) curiosity, etc. Regarding safety, no doubt you're 100% correct. We have a local VOR approach with a course change at the FAF and a high descent gradient on final. Without descending immediately pass the VOR, the odds of getting in shrink rapidly. |
#18
|
|||
|
|||
VOR approach- when to descend from the FAF
Peter wrote:
For what this is worth, on the European IR one is not supposed to descend (from the platform altitude) unless one is established within 5 degrees of the track. I don't know the reference but this is what I was always taught. To me, it makes sense and the only time I would deviate from it would be ICAO standards for "established" are 1/2 scale deflection. The US doesn't have a similar definition, unfortunately. Sam Spade was arguing that, over the VOR, that standard doesn't have much meaning. For a staying-in-protected-airspace point of view, I'm sure he's correct. |
#19
|
|||
|
|||
VOR approach- when to descend from the FAF
On Feb 19, 2:53*pm, Les Izmore wrote:
This is being treated like some kind of academic angels-on-the-head-of-a-pin question. *It is not. It is academic. Two choices, very simple. Either you are on the final approach course, or not. If not, you go missed, nothing complicated. They usually "try harder" *to reintercept the course while going still lower. *This practially always ends up in a situation that could be disastrous in actual conditions. Then that pilot is behind the plane. See above for choices of action. Really very academic. It may not be a training issue, but a currency issue, thus the IMPORTANCE of staying current. and I base that opinion on watching a lot of pilots, many of them experienced and *instrument rated, screw approaches up pretty badly, for any number of reasons. At anytime a pilot "screws up" as you alleged, missed is always that option. Very academic. I personally experience quite the opposite for IA pilots when I was their safety pilot, they get it right and never gone full deflection. I am not a CFI by any means for what this is worth. I don't care what the "book" says. Book is very clear. If you are not on the final approach course within the established tolerances, you go missed. What part of the book is hard to understand? The orignal question is a very elementary question for IA flying. For what it's worth, in my 600 hours of instrument flying, it takes a hell of a lot more then 1 or 2 miles for the CDI to start moving. If that is happening to the original poster, or you experienced that, then there is something wrong with that station signal or airplane equipment and a missed approach is in order. KMBO has the VOR alpha approach and I can pick up the VOR signal strong on both my NAV1 and NAV2 within 20 miles. When you are within 1 or 2 miles of a final approach fix (I.E. VOR) it is normal to get a full deflection from that "zone of confusion" for the CDI. The needles will recapture within a mile or two of station passage. But you do not descend before getting the from flag on your NAV1 or NAV2 AND being on the final approach course. If you don't get a from flag you go missed even if you are on the final approach course as something is radically wrong equipment wise.. Note the word AND, both being on the approach course AND from flag, BOTH must be present. VERY SIMPLE! The original question was so basic, that it sounded like an Mx question.. Allen |
#20
|
|||
|
|||
VOR approach- when to descend from the FAF
Greg Esres wrote:
Peter wrote: For what this is worth, on the European IR one is not supposed to descend (from the platform altitude) unless one is established within 5 degrees of the track. I don't know the reference but this is what I was always taught. To me, it makes sense and the only time I would deviate from it would be ICAO standards for "established" are 1/2 scale deflection. The US doesn't have a similar definition, unfortunately. Sam Spade was arguing that, over the VOR, that standard doesn't have much meaning. For a staying-in-protected-airspace point of view, I'm sure he's correct. Correct. The protected airspace for a VOR IAP overhead the VOR when it's the FAF is 1 mile each side of the station. This width expands as the aircraft departs the VOR/FAF. The maximum course change permitted at the VOR/FAF is 30 degrees. Descent shouldn't be made unless the pilot is tracking on course inbound to the VOR/FAF. If he is on course as station passage occurs, and a course change is required, a turn to intercept while commencing descent is expected in the design of the criteria; i.e., the descent gradient is calculated from the VOR/FAF, not from some imaginary post-facility point of intercept, and the maneuver required to reintercept is minimal assumming reasonable comptetency. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Garmin 430 rquestion- does the approach always have to be activated via "activate approach"? | Terence Wilson | Instrument Flight Rules | 46 | February 18th 08 05:46 PM |
When to descend II | Dan Luke[_2_] | Instrument Flight Rules | 76 | November 27th 07 08:12 PM |
When to descend | Dan Luke[_2_] | Instrument Flight Rules | 44 | October 14th 07 09:12 AM |
VOR approach SMO | Robert M. Gary | Piloting | 124 | August 3rd 07 02:17 AM |
Completing the Non-precision approach as a Visual Approach | John Clonts | Instrument Flight Rules | 45 | November 20th 03 05:20 AM |