Plet RNAV Revisited

RNAV, GNSS, GPSS. Your place to discuss all aspects pertaining to Instrument Flying.

Moderator: Moderators

User avatar
Hop Harrigan
1k poster
1k poster
Posts: 1230
Joined: Tue Jun 01, 2010 7:55 pm
Has liked: 10 times
Been liked: 66 times

Plet RNAV Revisited

Unread post by Hop Harrigan » Sat Sep 04, 2021 8:35 pm

HI,
So I’m looking at the Plet RNAV Rwy30 chart (attached) in light of an approach in pretty heavy weather on Monday...
For an approach from the NE over the mountains, the MSA diagram shows:
Not below 6700’ from 25nm - 10nm
Not below 4800’ from 10nm to the airfield.
The two possible entry points from this heading are EGMAB and GENUV. EGMAB and GENUV are 9.1nm and 12.6 nm from the field respectively making it impossible to stay above the MSA and still intercept the entry point at 4200’.So it seems impossible to legally do this approach without first doing a descent in the hold. Additionally there is NO hold available at EGMAB.
So of how much use is this approach if one is going to fly it in IMC and how legal is it in IMC or VMC?
I suppose a high ROD approach from EGMAB at 4800’ to the IF at 2800’ is possible although not a great idea in IMC. It seems that this RNAV approach is no less work than the old NDB approach.
Any ideas?
Hop
F9DAE8E3-7A5D-498D-BFA4-82ACE3C757B2.png
You do not have the required permissions to view the files attached to this post.
There is no gravity...the Earth sucks
User avatar
Hop Harrigan
1k poster
1k poster
Posts: 1230
Joined: Tue Jun 01, 2010 7:55 pm
Has liked: 10 times
Been liked: 66 times

Re: Plet RNAV Revisited

Unread post by Hop Harrigan » Sun Sep 05, 2021 9:01 am

ps...if any of the Cemair or other pilots are listening...pls could you let me know how you guys handled this RNAV approach in IMC
Thanks
Hop
There is no gravity...the Earth sucks
final_approach
Priming
Posts: 39
Joined: Thu Mar 22, 2018 2:37 pm
Closest Airfield: East Africa
Has liked: 0
Been liked: 7 times

Re: Plet RNAV Revisited

Unread post by final_approach » Sun Sep 05, 2021 3:36 pm

Hi Hop,

It really helps to slow down during rnav approaches and at 120kts that 5 miles will take 2.5 mins with the required rate of 660fpm from 4800 down to 2800 feet. Other option is to overfly the airport and do the approach from UNGOR. I generally take flap before the iaf and configure fully before the iaf. Works like a charm
User avatar
Hop Harrigan
1k poster
1k poster
Posts: 1230
Joined: Tue Jun 01, 2010 7:55 pm
Has liked: 10 times
Been liked: 66 times

Re: Plet RNAV Revisited

Unread post by Hop Harrigan » Sun Sep 05, 2021 5:18 pm

Thanks f_a,
Am leaning towards just doing single hold then into the approach. Might calm things down by taking a little longer track
Hop
There is no gravity...the Earth sucks
final_approach
Priming
Posts: 39
Joined: Thu Mar 22, 2018 2:37 pm
Closest Airfield: East Africa
Has liked: 0
Been liked: 7 times

Re: Plet RNAV Revisited

Unread post by final_approach » Sun Sep 05, 2021 5:30 pm

What A/C are you taking there? I prefer the longer final as those flyby points sometimes catch you by reducing the the track miles to touchdown.
DipStick
Take off Clearance
Posts: 138
Joined: Mon Dec 07, 2009 11:25 am
Closest Airfield: FAWB
Location: Pretoria
Has liked: 3 times
Been liked: 0

Re: Plet RNAV Revisited

Unread post by DipStick » Sun Sep 05, 2021 10:36 pm

Hi there,

EGMAB has a restriction of 4200' or above, there is no requirement to be at 4200' at EGMAB.

As final_approach mentioned, it's best to slow down and configure as early as possible, most GNSS approaches are designed for continuous descent all the way to the runway.

Calculate your descent rate required, a good rule of thumb for a 3° slope is (GS x 10 / 2).
Plan to be at PG2F1 at 1500' which gives you 500' until you need to be approach stable.

The plate also has a table of altitude required versus distance from threshold, this is very useful to check your heights as you descend.

Also be careful of your distance out to sea in a single engine aircraft.

Hope this helps.
Last edited by DipStick on Mon Sep 06, 2021 10:22 am, edited 1 time in total.
Aidan J Mills
ATPL
B737-800
L410
PC12
C208
PA34

Aviate, Aviate, Aviate, Navigate, Communicate

Look outside, lest you miss the main event!
User avatar
Iceberg
Too Tousand
Too Tousand
Posts: 2977
Joined: Mon Sep 05, 2011 1:09 pm
Closest Airfield: FAWB
Location: Pretoria
Has liked: 78 times
Been liked: 181 times

Re: Plet RNAV Revisited

Unread post by Iceberg » Mon Sep 06, 2021 8:28 am

I'll do something similar to what Dipstick recommends. Arrive at EGMAG slowed down and configured and use a higher ROD than normal to arrive at PG2F1 at 1500 ft.

If the high ROD is not desired, route to GENUV from EGMAG and do a teardrop back to GENUV, descending all the while to arrive back at GENUV ready for the final phase of the approach.
The sky is not the limit....
ZS-MDK
Karl Eschberger
User avatar
Hop Harrigan
1k poster
1k poster
Posts: 1230
Joined: Tue Jun 01, 2010 7:55 pm
Has liked: 10 times
Been liked: 66 times

Re: Plet RNAV Revisited

Unread post by Hop Harrigan » Mon Sep 06, 2021 9:27 pm

I’m flying an SR22 certified for RNAV as am I. I use an approach speed on the RNAV of 120-130 kts (unless ATC has other ideas) and an ROD of 700’/min nominal.
The problem at Plet is the 6700’ MSA all the way in to 10nm while the RNAV entry point is at 9.1nm (from the af). I agree going out to sea and looping back could work but it is a long way off the coast. Think I’ll stick to the published hold.
Coastal weather yesterday was forecast as sheit...not sure if the weather was or the forecast was...so going tomm although low icing levels add to the problem of the approach ROD. Guess the anti-ice will earn it’s keep.
Thanks for the advice guys!
Hop
There is no gravity...the Earth sucks
User avatar
Hop Harrigan
1k poster
1k poster
Posts: 1230
Joined: Tue Jun 01, 2010 7:55 pm
Has liked: 10 times
Been liked: 66 times

Re: Plet RNAV Revisited

Unread post by Hop Harrigan » Mon Sep 13, 2021 4:23 pm

Right...so now I am totally confused!
When I bring the Plet RNAV approaches up on the NavCom, the HOLD’s appear at the END of the approach! As though it’s only intended as a hold after a missed approach. So how the heck do you get down from the MSA to the start of the RNAV approach?
Is this a mistake or am I suffering from hypoxia?
Hop
There is no gravity...the Earth sucks
User avatar
Iceberg
Too Tousand
Too Tousand
Posts: 2977
Joined: Mon Sep 05, 2011 1:09 pm
Closest Airfield: FAWB
Location: Pretoria
Has liked: 78 times
Been liked: 181 times

Re: Plet RNAV Revisited

Unread post by Iceberg » Mon Sep 13, 2021 4:40 pm

Hop Harrigan wrote:
Mon Sep 13, 2021 4:23 pm
Right...so now I am totally confused!
When I bring the Plet RNAV approaches up on the NavCom, the HOLD’s appear at the END of the approach! As though it’s only intended as a hold after a missed approach. So how the heck do you get down from the MSA to the start of the RNAV approach?
Is this a mistake or am I suffering from hypoxia?
Hop
Hop, I think you are overthinking this. The holds are there for convenience and safety. For example if there is another aircraft already doing the approach you can enter one of the holds and then descend into the approach when it is safe. Otherwise slow the aircraft right down, cut the power, prop(s) fully fine and do a nice constant high ROD to the FAF. Obviously after a missed approach, the holds are there to return to a safe space and think about what comes next - maybe another try or divert to George/PE etc.
The sky is not the limit....
ZS-MDK
Karl Eschberger
User avatar
Hop Harrigan
1k poster
1k poster
Posts: 1230
Joined: Tue Jun 01, 2010 7:55 pm
Has liked: 10 times
Been liked: 66 times

Re: Plet RNAV Revisited

Unread post by Hop Harrigan » Mon Sep 13, 2021 5:33 pm

Hi Karl,
I have seen other RNAV approach plates (on the Garmin manual and video) that are used as entry holds to the procedure. So figured this was similar.
As far as the slow, high ROD transition from the MSA to GENUV is concerned, the end of the MSA and GENUV are only 0.9nm apart (MSA is measured from FAPG). You then need to descend from 6700’ to 4200’ in 0.9 nm. That’s 2500’ in less than one minute. Quite an ROD!
Of course you can cross GENUV much higher and try to descend onto the glide slope as you approach but it’s not a very stable approach method in my opinion.
I guess it’s also possible to ‘create’ your own RNAV hold at GENUV. However it seems a bit like a lost opportunity not getting this sorted first time around.
I did wonder if JEPPESEN maybe misinterpreted the plate and put the hold at the wrong end of the procedure?
Hop
There is no gravity...the Earth sucks
User avatar
Iceberg
Too Tousand
Too Tousand
Posts: 2977
Joined: Mon Sep 05, 2011 1:09 pm
Closest Airfield: FAWB
Location: Pretoria
Has liked: 78 times
Been liked: 181 times

Re: Plet RNAV Revisited

Unread post by Iceberg » Tue Sep 14, 2021 12:11 pm

Hop Harrigan wrote:
Mon Sep 13, 2021 5:33 pm
Hi Karl,
I have seen other RNAV approach plates (on the Garmin manual and video) that are used as entry holds to the procedure. So figured this was similar.
As far as the slow, high ROD transition from the MSA to GENUV is concerned, the end of the MSA and GENUV are only 0.9nm apart (MSA is measured from FAPG). You then need to descend from 6700’ to 4200’ in 0.9 nm. That’s 2500’ in less than one minute. Quite an ROD!
Of course you can cross GENUV much higher and try to descend onto the glide slope as you approach but it’s not a very stable approach method in my opinion.
I guess it’s also possible to ‘create’ your own RNAV hold at GENUV. However it seems a bit like a lost opportunity not getting this sorted first time around.
I did wonder if JEPPESEN maybe misinterpreted the plate and put the hold at the wrong end of the procedure?
Hop
You don't have to be at GENUV at 4200 ft. Just not below. So if you get there at 5000ft you still have plenty of time and distance to get to the FAF at 1500 ft. It is a non-precision approach, so there is no glideslope, just minimum heights at points on the approach.

Besides, the MSA is not cast in stone. Also if you draw a line at 110 degrees from the field - south of that the MSA is only 2700 ft. You are relying on your GPS for navigation after all, so if you cross the coastline I see no reason why you can't start the descent to GENUV. Once you cross the 110 degree radial you definitely can.

My Jepp plates reflect your plate accurately.
The sky is not the limit....
ZS-MDK
Karl Eschberger

Return to “Instrument Flying”