When I posted earlier that the underlying navaid has to be displayed somewhere I of course meant only in the case of an NDB, VOR, or LOC type of approach. On a GNSS approach one would just use the FMS as usual.
I have been taught to fly NPA’s as What Next wrote, and I use the VS on the autopilot and make slight adjustments.
I just did last week my initial MEP/IR checkride/exam (after having had my SEP/IR for some time now).
GPS usage:
As for the use of GPS equipment on e.g. a VOR/DME or NDB/DME approach: I was allowed to use all available instruments including the GPS, but would have to have the VOR or other classic instruments tuned as well and identified if I were to fly e.g. an NDB or VOR approach.
Approach names:
On a side track: for whatever reason, approaches that used to be called e.g. the VOR/DME approach RW 05 are now changed (on request of ICAO) on the Jepp charts to just the VOR RW 05 (without the DME) and also ATC uses these new names (without e.g. the DME). Not sure why. I was also allowed to fly the RNAV overlay SID instead of the “classic” one, but he wanted me of course to also demonstrate that I was capable of using the classic instruments. On wanting to fly the RNAV SID (overlay) I had to show him I had the appropriate RNAV SID (overlay) chart available and not the classic one. I had, so no issue. In that case, the turn after e.g. × DME on the classic SID could come later on the RNAV SID and I would have to wait until getting the turn command from the GPS.
Flying NP approaches:
On briefing the approach while I was inbound and ready for the approach, the examiner asked at which speed I was going to fly the approach. There he is looking for IAS as you ALWAYS (in my humble opinion) fly indicated airspeed. However, to calculate the rate of descent for e.g. a 3 degrees glide path, I would use either (a) a rate-of-descent formula (in ft/min) of 5 x GS + 8% or (b) look at the approach plate where the table there indicates GROUND speeds versus rate of descent in ft/min. So, the examiner was looking at the DME instrument to check the ground speed and then calculated the glide path from that, but was still expecting me to fly IAS. Then as Achim indicated, you would correct your rate of descent on each NM check keeping the IAS at the approach speed I indicated I would fly the approach and then adjusting a little bit along the way. If I needed a larger rate of descent I would also have to watch my IAS as that one had to remain stable.
I have the feeling that starting to fly GS or something like that could be dangerous.
AeroPlus wrote:
a rate-of-descent formula (in ft/min) of 5 x GS + 8%
Why the +8%?
That is what was in the IR syllabus of the training school (+8%), but I personally use 5% of the GS and for timing 320 feet per NM on a standard 3% glide path.
I use GS x 5 and 300 ft per NM … somehow my (already bad) math doesn’t work well in the airplane.
Half your ground speed and add a 0 to the end. I can’t multiply by 5…
Ps I use 5 x GS and plate VS as well. On my IRT wind was calm which was actually harder work than strong wind I found!
Varying IAS would just lead to an unstable approach in a big jet surely especially with inherent speed instability away from target Apporach speeds? Even in a light twin increasing IAS could put you close to gear and flap limits?
AeroPlus wrote:
That is what was in the IR syllabus of the training school (+8%)
Did they tell you why? The exact ratio of VS in fpm to GS in knots for a 3° glideslope is about 5.3, so If you wanted the exact VS you should add 6%. But there is no point in trying to achieve that kind of precision as GS will change during the approach in any case.
Most instructors and examiners don’t like people asking too many questions. I have in the past always been the person that wanted to know the WHY. Now I have been doing a lot of IFR flying, but for the MEP I had to go through an initial MEP/IR skills test doing it all as I also learned to do it when I just started flying IFR and went for the initial SEP/IR skills test. So, I opted to just go along with them which is already quite difficult as one instructor to another examiner might have a completely different view on how things MUST be done (according to them) such as when to lower the gear and you name it. So, my short answer: no, they did not tell me why 8% and I also did not ask :-)
