Interesting reading your flight testing.

I can’t offer a great deal of insight as all the 748s I flew , which presumably had the same or very similar autopilot systems to the F27 had the autopilots in an unserviceable state. They’d broken at some point and the operators didn’t think it was a worthwhile use of resources to fix them. 
I did fly a couple of  series 2B 748s in 1996 which had serviceable, and compared to the series 1 and 2A versions, more advanced autopilots which also had  a flight director system and even an HSI and colour ADI.
I remember thinking it was almost state of the art in comparison to the instruments in the older series 1s and 2As which were quite literally off of Lancaster bombers.

Edited December 30, 20241 yr by jon b

14 hours ago, jon b said:

Whenever I fly to Delhi and I see the old HAL 748 they have parked up there , I always think of your ice cream story 🙂

I miss them so! Fly safe Jon!

C

1 hour ago, jon b said:

which presumably had the same or very similar autopilot systems to the F27 had the autopilots in an unserviceable state

Then they are modelled in the sim pretty well then!

Appreciate any input from pilots of similar aircraft. I've always been on a personal mission to seek out and restore/keep running planes and systems in the sim that are fairly accurate to the real world. It is a losing battle sadly but it helps if you can install what is realistic and what is not, then work around that.

The older the plane, the less I'm inclined to use an ap at all but when you do a long trip having heading and alt hold is very useful. In this sim plane those work well, the speed hold and vor tracking less so, but at these leisurely cruise and climb speeds you have plenty of time to do it yourself.

I would love to read how the autopilot in the 70's classic jets handled mach speed vor intercepts! I have trouble in the F28 due to compromised sim ap modelling but....after your comments I can adjust I guess by just assuming the ap is out of service for lateral nav!

Ok off to do the last test of original version now, which ironically takes me over the Andes using same VORs and altitude as Flight 571. Very similar plane too! I'll have my else glued to the DME before I make that Curico turn though...

Yes we used to fly these things on 1 to 2 hour legs and between 4 and 6 sectors a day all without the autopilot working.

And doing that on night freight in the pitch black with stormy winter weather, all raw data needle work too, not even an HSI , it soon made a man of you ! The freighters didn’t even have heating, you had to fly in a coat, hat and gloves in winter!

Kids today, straight onto an A320, don’t know they’re born etc etc….

 

Phew! Well I did the final test. Amazing flight. Will write up results later after a break but definitive answer is original version has far superior VOR behaviour. Will not be updating to the GPS enabled version for sure. Perfect NAV 1 intercepts from all directions and angles, 'ghost' NAV 2 intercept.

https://imgur.com/gallery/andes-crash-1972-flight-571-vor-route-fokker-f27-VFi2DuN

Flew past the exact sport flight 571 took a wrong turn into the valley.

 

Here is the valley they flew down into. 99% sure from a lot of research. Correct me if I'm wrong!

 

I just discovered this gem! Now this is proper aviating!

 

I'm having issues with getting the plane started up and have the radio's and instruments working. If i just start and the runway all systems are working as normal. Probably needs some time to go over the manual to solve it. 

I am flying in 2024 by the way but so far no issues. Currently I've only flown the vanilla version, so next is the texture and liveries. 

 

Eventually i'll get up to the level of the KLU F27 Demo flight... intentionally or unintentionally 😋  (pilots talk dutch during the demo (2nd half of the video) but they mention hitting 2G in the turns)

 

Thanks for your extensive testing! I've meant to fly the flight 571 route - your post has encouraged me to finally do it.

On 12/30/2024 at 1:32 PM, sloppysmusic said:

Even the Airbus apparently is not certified to allow raw vor precision approaches, only enroute nav.  I get that jets with INS/FMC systems do not have Cat III VOR capable systems as backup but the planes with ONLY VOR , like the F28 and 717 for example SHOULD have safe VOR capture close to transmitter (8-15 miles).

Just a short note on terminology: A VOR approach is considered to be a non-precision approach because it doesn't have vertical guidance (unlike an ILS). Also, "CAT III VOR" isn't a thing - "CAT III" relates only to ILS approaches.

Not sure which Airbus you're referring to - but all of them are definitely capable of flying VOR approaches without using the FMS. I believe the A300 and A310 autopilot have VOR tracking. Interestingly, the later Airbuses, starting with the A320, don't have VOR tracking capability in the autopilot. VOR approaches, if they aren't being flown in "managed" mode (i.e. with the FMS) are typically flown in TRK/FPA mode on the autopilot, which maintains a given track and flight path angle. The track and FPA are adjusted manually to keep the aircraft on the desired approach path.

54 minutes ago, martinboehme said:

CAT III" relates only to ILS approaches.

by VOR I mean all similar systems VOR/LOC/ILS! (Everything that uses the regular NAV 1 and NAV 2 radios basically. ADF not important as no AP tracking there (again obviously Im not talking about flying direct to one or getting a fix from one in an FMS!)

I rad a spec sheet for the F28 saying it was Cat II certified to xxx mins I will try to find it.

The airbus quote was from an Airbus pilot I believe in one of those links above.

The quote was yes they can track but the AP was not certified to fly using them. I am quoting an 'expert' here not my own direct knowledge.

Edited December 31, 20241 yr by sloppysmusic

I. Model  F28 Mark 0100 F28 Mark 0100, application for Type Certificate on March 25, 1983;   approved November 20, 1987 The F28 Mark 0100 (based on the F28 Mark 4000) has two Rolls‐Royce Tay high by‐pass ratio engines with thrust reversers; extensive use of composites; increased fuselage length by 18.83 feet with plugs forward and aft of the wing; increased wing span by 9.8 feet; increased wing chord and improved aerodynamics with extended leading and trailing edges; increased horizontal stabilizer span by 4.6 feet; new flaps, larger ailerons, strengthened landing gear with new wheels and brakes; increased passenger count from 85 to 109 in the basic version; increased maximum weights; advanced digital electronic flight deck with integrated flight management system; autopilot/flight director, including CAT III autoland capability, and thrust management system; electronic flight instrument displays and full ARINC avionics. Fuel capacity, max operating speed and maximum operating altitude remain the same

https://www.easa.europa.eu/bg/downloads/7450/en

My mistake Cat III AND autoland :D but with FMS so different nav. Sure I had a CAT II cert somewhere else for older systems.

Edited December 31, 20241 yr by sloppysmusic

2 hours ago, sloppysmusic said:

by VOR I mean all similar systems VOR/LOC/ILS! (Everything that uses the regular NAV 1 and NAV 2 radios basically.

Ah, got it!

2 hours ago, sloppysmusic said:

The airbus quote was from an Airbus pilot I believe in one of those links above.

I've found the quote, it was about the A300-600:

"Javelin,the A300-600 has a vor/loc button.The Fcom states that the vor tracking is for enroute nav only,and has variour other restrictions on speed/intercept etc.In other words it is rubbish!!"

Which I find interesting, as the A300-600 was otherwise technologically quite advanced - and in particular, it was CAT III autoland capable.

8 minutes ago, martinboehme said:

it was CAT III autoland capable.

With FMS/GNS/INS? NOT backup systems I believe? Some of that reading is very enlightening!

Another thing I've found with the original AP is the interception seems to be so advanced and useful in different situations that it seems to be maybe not like IRL? TOO good lol?
I am trying to find system level AP/VOR manuals/specs no luck yet.

example. The V1 will intercept at ANY angle at a sensible distance but will not turn until it senses the needle moving, unlike the WT GPS one that will always turn ac 45 degrees towards the VOR even if you are 10/50/100 miles away.

I just did a flight in v1 again which I'm really enjoying now as the ONLY truly 'pure' VOR plane in MSFS that I can confirm has no gps issues and lost my approach vor so used another nearby then it turned up 15 miles out so I used that to intercept and it did a turn at 30 degree intercept which threw spanner in my earlier statement...then hmmmm. I think the VOR was wrongly input into sim as a LOC hence the different intercept?! It would explain different behaviour. There is no similarity between the v1 and the v2 vor behaviour. v2 is strictly LNAV based. It plots a smooth intercept like LNAV would but does NOT give you the option that you NEED with vor to do a fly over waypoint and NOT bypass for altitude safety.

All this talk of autopilots reminded me of a flight on the jump seat of an Air Anglia FK27 between EGPH and LFPO in the late 70s.

Air Anglia required their pilots to handfly the aircraft and had deliberately removed all Autopilots. That surprised me and wasn't exactly welcomed by the crew.

On the return flight we made a surprisingly spritely climb to FL230  There was more performance that I'd anticipated even with a decent load.

Nice aircraft and a nice airline.

30 minutes ago, nippa said:

There was more performance that I'd anticipated even with a decent load.

 Maybe for some reason they stopped caring so much about saving company fuel. Can't think why? 

2 hours ago, sloppysmusic said:

2 hours ago, martinboehme said:

it was CAT III autoland capable.

With FMS/GNS/INS? NOT backup systems I believe?

There's a relevant quote in that PPRuNe thread:

"The A300 is quite susceptable to loc deviations due to ac on the rwy and departing-Airbus came up with a localizer inertial smoother to sort it out but my company didn't buy it."

So at least originally there was no input from the INS, and on an autoland, interference from other aircraft bending the ILS beam wouldn't be an issue because other aircraft aren't allowed near the runway in low visibility procedures.

I'm also pretty sure the input from the INS (if indeed it was the INS and not some independent inertial reference system) wouldn't have taken the form of an absolute position, as the INS position is far too inaccurate for that, but probably a velocity vector. I'm guessing that if the localizer signal changes quickly but the velocity vector is still pointed down the centerline, the aircraft would delay its response to the localizer deviation because it would "know" that it has to be spurious.

2 hours ago, sloppysmusic said:

Another thing I've found with the original AP is the interception seems to be so advanced and useful in different situations that it seems to be maybe not like IRL? TOO good lol?

I think so too. I've read various descriptions of early autopilots saying that pilots would prefer to do the intercept themselves and only select VOR mode on the autopilot once they were established on the radial.

2 hours ago, sloppysmusic said:

v2 is strictly LNAV based. It plots a smooth intercept like LNAV would but does NOT give you the option that you NEED with vor to do a fly over waypoint and NOT bypass for altitude safety.

You wouldn't typically keep VOR mode switched on anyway when overflying a VOR. Instead, a few miles before the VOR, you would switch to heading mode, turn to the new radial in heading mode when overflying the station, then switch back to VOR mode once you're established on the outbound radial. This is because VORs have a "cone of silence" (also referred to more dramatically as the "cone of confusion") where the signal becomes unreliable once close to the station.

At least this is what I was taught in my VFR training on VOR navigation, and we were using the G1000, which has a very capable autopilot.

1 hour ago, martinboehme said:

You wouldn't typically keep VOR mode switched on anyway when overflying a VOR.

Yes I understand that well lol I was referring to a manual WAYPOINT as in intersecting a route BETWEEN 2 vors or to just intercept radial say 75 miles out., or outbound from one and turn 90 left at my decided intercept between them (use dme to know when near)