Difficult Approach

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GaryRR
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Difficult Approach

Post by GaryRR »

Was flying V35 N41G from Columbia, SC KCAE to Atlanta Peachtree. I was VFR but I checked Dekalb Metar to get a read on which runway would be active and I guessed 3R correctly. I called Dekalb Tower about 20nm out and recieved clearance for 3R. Right traffic pattern. I put the approach into the 530 to enter pattern at the initial approach fix. I had no idea it was such an obtuse approach though. From FAF it is turn right to heading 026 and boom, the runway is right there. I made the rookie error of focusing too much on the pattern LNAV and too little on the pattern VNAV. I crossed FAF and was still at 150 knots. I dropped my gear and went flaps one. I was right of the centerline and went to adjust with left rudder and went for flaps full down and the Bonnie did NOT like that. She rolled turtle to the left and I ended up nose down in a residential area near the airport. Very frustrating after what was a good flight out of Columbia.
My take away lesson is that when I realized I wasn't trimmed for final I should have called missed approach and gone around better informed about the pattern. Or. I should have studied the Flight Aware Plates a little more closely. IRL I would dead.
Edit. After going back and studying the plate I realize the approach is circling as is due to terrain. I had no idea the Atlanta area was that mountainous.
I will take my lessons on the next hop of my Orbx Airports Southeastern US tour. Next destination is Pigeon Forge/Gatlinburg. Gaurenteed I will study up for that one. There are definatley mountains there.

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AKar
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Re: Difficult Approach

Post by AKar »

All that I can find for 3R is an RNP approach, something a typical GA has no business flying in the first place. :D Of course, in the sim just about everything can be attempted, and can be lots of fun.

-Esa

GaryRR
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Re: Difficult Approach

Post by GaryRR »

Well, isn't that the same as a GPS WAAS approach? Many airports have them. My local, KSEG Selinsgrove PA has two and a VOR approach. I know the area well. I can eyeball it just fine.

GaryRR
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Re: Difficult Approach

Post by GaryRR »

AKar wrote: 17 Jun 2022, 06:14 All that I can find for 3R is an RNP approach, something a typical GA has no business flying in the first place. :D Of course, in the sim just about everything can be attempted, and can be lots of fun.

-Esa
Okay. I did some homework. It turns out that IRL I would never have been granted clearance for Dekalb 3r with a Bonnie. I don't think what I'm equipped with can correctly follow an RNP Approach like that unless I let the 530 handle LNAV and myself control the descent. I may stay around Atlanta a little while to study this.

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AKar
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Re: Difficult Approach

Post by AKar »

No, RNPs are different from GPS or LPV approaches. It has been some years since I last refreshed myself on such topics, but basically RNPs require you to have an FMS capable of navigation accuracy estimations and dual GPSes. (There could be other acceptable setups as well.) What is behind the requirements is a system capable of detecting, among the other things, any issues with the navigation accuracy so that the flight crew is alerted of degraded navigation, and also so that events such as complete loss of GPS signal or derived position integrity does not prevent executing the missed approach procedure safely.

On the flip side, RNP approaches allow for more complex flight paths, such as RF legs, with reduced distances from terrain features in comparison to classic instrument procedures.

-Esa

GaryRR
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Re: Difficult Approach

Post by GaryRR »

Yes. They are interesting. But I'm sure 3R would never be authorized for a classic GA piston IRL. I had no idea Atlanta was in such hilly terrain. But that is the exact reason Dekalb has two RNP approaches. Dekalb is a Hartsfield reliever I think and I believe many of the big corporations in Atlanta base their aircraft there although my company, the More Saving More Doing home improvent retailer bases at Fulton County Airport. 5 Dassault Falcons for Heavens sake.

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Orlaam
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Re: Difficult Approach

Post by Orlaam »

This post intrigued me. I hadn't flown into KPDK before and wasn't familiar with the plates. I went down a rabbit hole on the definition of RNP over GPS/RNAV approaches. RNP appears to be more precise without using an ILS. It seems to have radial fixes between the waypoints and therefore provide stricter turns for terrain or obstacle clearance. This makes sense when looking at a route between mountains, such as the ZUNZ approach to RWY 23. There is certification required and dual WAAS-equipped standards to achieve this. Nevertheless, even without a preprogrammed RNP into RWY3R, I entered each waypoint into the GTN750 and flew the route in both the Comanche and Bonanza. I used the AP more in the Bonanza because it handles turns and vertical navigation much better. I used heading mode and careful trimming in the Comanche. I also turned off the AP much earlier on the Comanche due to a lack of AP efficiency. In visual conditions it seems not unlike a standard extended downwind to base. You are approximately 5 nm parallel to the runway on downwind and close the gap in the turn to base. To me, this seems like a standard visual approach with a wider pattern, albeit still within KPDK airspace. You are well away from KATL too. Obviously, in low visibility you wouldn't attempt this, but in good visual conditions it seems fair to use those waypoints as a guide. I watched an approach to runway 3 in a Swearingen Metroliner, performed at night using a downwind and base to final approach. It seemed all visual, however, it was as if the distance was similar to that of the RNP waypoints would plot you.

I often wonder if any pilots use ForeFlight to aid them on an approach they aren't certified to fly. IOW, this approach is drawn perfectly in the ForeFlight map, thus using it as an aid for visual guidance helped. Of course, in visual conditions you don't need true guidance in a pattern with VFR, but in the sim it helps when you have no peripheral vision to judge turns to base and final. KABQ has RNP approaches like this, and they are sketchy with a larger jet. I wouldn't trust them very much in low visibility. KSDL also has an RNP into 21 that looks a lot like the standard visual you would see them do normally. KSDL and KABQ both provide mountain avoidance however, but I am unclear about your remark about KPDK having terrain to avoid. There is one small mountain about 7.7 nm southeast of KPDX at 688 feet above KPDX's elevation. Aside from that, ATL is really flat land. :?
Chris J.

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AKar
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Re: Difficult Approach

Post by AKar »

Orlaam wrote: 21 Jun 2022, 03:43 It seems to have radial fixes between the waypoints and therefore provide stricter turns for terrain or obstacle clearance.
In this case yes, though not all RNP approaches use RF legs (Radius-to-Fix). Note that the plate specifically mentions that RF is required. This is because not all flight guidance systems are capable of tracking through RF legs, but instead use turn prediction which is based on the angle between track-in and track-out, ground speed and some other factors. Indeed, this is even more true for flight sim aircraft, even PMDG at least didn't use to do proper RF, but internally added some waypoints along the path as 'gates' for the plane to fly through instead. Not sure if their current MSFS-era offerings still do this, or if they have enhanced their navigation simulation since.

Of note is also that the use of RF legs is not technically limited to RNP approaches, they can be found in other terminal procedures as well, and Garmin's GTN and GNS series are generally RF capable - both in real life and as trainers behind RXP simulation. Yet, being RF-capable does not equal to being RNP-capable.

-Esa

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Orlaam
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Re: Difficult Approach

Post by Orlaam »

Needless to say, it's all very confusing considering what it is, lol. I don't know if PMDG or other other big players in MSFS are including this either. I have yet to be able to afford a computer that'll give me MSFS performance. Hopefully soon. 8)
Chris J.

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AKar
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Re: Difficult Approach

Post by AKar »

Yeh, while the RF legs are somewhat of a novelty as a common thing for the procedure to come up with, the building blocks of instrument procedures often contain their elderly relative: AF leg, or Arc-to-Fix. This is the familiar DME arc that has been around for years in many approaches and departures.

-Esa

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Orlaam
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Re: Difficult Approach

Post by Orlaam »

I like the older approaches and navigation methods, but using GPS has spoiled me, and I just don't mess with them anymore.
Chris J.

Asus Maximus VII Hero motherboard | Intel i7 4790k CPU | MSI GTX 970 4 GB video card | Corsair DDR3 2133 32GB SDRAM | Corsair H50 water cooler | Samsung 850 EVO 250GB SSD (2) | EVGA 1000 watt PSU | Windows & Pro 64 bit | FSX:SE

GaryRR
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Posts: 353
Joined: 26 Dec 2020, 22:32
Location: KSEG Selinsgrove, PA

Re: Difficult Approach

Post by GaryRR »

Orlaam wrote: 21 Jun 2022, 03:43 This post intrigued me. I hadn't flown into KPDK before and wasn't familiar with the plates. I went down a rabbit hole on the definition of RNP over GPS/RNAV approaches. RNP appears to be more precise without using an ILS. It seems to have radial fixes between the waypoints and therefore provide stricter turns for terrain or obstacle clearance. This makes sense when looking at a route between mountains, such as the ZUNZ approach to RWY 23. There is certification required and dual WAAS-equipped standards to achieve this. Nevertheless, even without a preprogrammed RNP into RWY3R, I entered each waypoint into the GTN750 and flew the route in both the Comanche and Bonanza. I used the AP more in the Bonanza because it handles turns and vertical navigation much better. I used heading mode and careful trimming in the Comanche. I also turned off the AP much earlier on the Comanche due to a lack of AP efficiency. In visual conditions it seems not unlike a standard extended downwind to base. You are approximately 5 nm parallel to the runway on downwind and close the gap in the turn to base. To me, this seems like a standard visual approach with a wider pattern, albeit still within KPDK airspace. You are well away from KATL too. Obviously, in low visibility you wouldn't attempt this, but in good visual conditions it seems fair to use those waypoints as a guide. I watched an approach to runway 3 in a Swearingen Metroliner, performed at night using a downwind and base to final approach. It seemed all visual, however, it was as if the distance was similar to that of the RNP waypoints would plot you.

I often wonder if any pilots use ForeFlight to aid them on an approach they aren't certified to fly. IOW, this approach is drawn perfectly in the ForeFlight map, thus using it as an aid for visual guidance helped. Of course, in visual conditions you don't need true guidance in a pattern with VFR, but in the sim it helps when you have no peripheral vision to judge turns to base and final. KABQ has RNP approaches like this, and they are sketchy with a larger jet. I wouldn't trust them very much in low visibility. KSDL also has an RNP into 21 that looks a lot like the standard visual you would see them do normally. KSDL and KABQ both provide mountain avoidance however, but I am unclear about your remark about KPDK having terrain to avoid. There is one small mountain about 7.7 nm southeast of KPDX at 688 feet above KPDX's elevation. Aside from that, ATL is really flat land. :?
My comment about the terrain around KPDK was made strictly from looking at the approach plates from Flightaware. Flightaware is my normal go to for arrival and departure charts. Although I usually just use the native flight planner for Enroute navigation and manually set my plan up in the RXP530. I would love to use GTN but whenever I install GTN in the Bonanza I get random CTDs from a trainer conflict with atioglxx.dll. I have Radeon 580 8 gig. I want to swap out to a 2070 to be free of ATI open GL. I have GTN in the Alabeo C421, Carenado PA 31, and Flysimware Lear has duals and never a CTD. Only installed in the BO do I get CTDs. So, I use 530/430 stack instead. I figure more realistic anyway because a average BO owner may not justify 16k USD for a GTN. A rich one yes maybe.

GaryRR
Staff Sergeant
Posts: 353
Joined: 26 Dec 2020, 22:32
Location: KSEG Selinsgrove, PA

Re: Difficult Approach

Post by GaryRR »

AKar wrote: 22 Jun 2022, 02:46 Yeh, while the RF legs are somewhat of a novelty as a common thing for the procedure to come up with, the building blocks of instrument procedures often contain their elderly relative: AF leg, or Arc-to-Fix. This is the familiar DME arc that has been around for years in many approaches and departures.

-Esa
I remember FS2000 to COF there were still a lot of active DME transmitters across the US and I learned how to use them. I flew DME arcs and I had taught myself how to locate intersections with VOR and DME. I may start using old practices again for fun. RXP makes it too easy.

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AKar
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Re: Difficult Approach

Post by AKar »

GaryRR wrote: 13 Jul 2022, 06:42
AKar wrote: 22 Jun 2022, 02:46 Yeh, while the RF legs are somewhat of a novelty as a common thing for the procedure to come up with, the building blocks of instrument procedures often contain their elderly relative: AF leg, or Arc-to-Fix. This is the familiar DME arc that has been around for years in many approaches and departures.

-Esa
I remember FS2000 to COF there were still a lot of active DME transmitters across the US and I learned how to use them. I flew DME arcs and I had taught myself how to locate intersections with VOR and DME. I may start using old practices again for fun. RXP makes it too easy.
Yeah, DMEs are probably the last of the 'classic navaids' to go away, for two main reasons. First, they are a shared component with TACAN in countries inclined to use it. That would mainly include countries with current or historical USAF presence. And second, DME/DME is usually the preferred way to correct the FMS position for inertial navigation system drift when GPS is not available.

-Esa

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