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INS Area Navigation


Fraser Gale

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Hello all,

Has anyone else on here tried to use the INS for area navigation? 

There were Concorde procedures for this at both Heathrow and JFK, the most fun being the Canarsie approach at JFK. This involved waypoints being inserted for the turn and the touchdown point of the runway and allowing the AFCS to fly the approach in INS down to 500ft with the crew monitoring in "Rad" as usual. Both INS units had to be updating from two different VORs at the time to ensure accuracy and altitude was controlled by crew selection of ALT AQUIRE and VERTICAL SPEED mode. 

The thing is, when I try to fly these approaches, the INS switches legs too quickly and too far away from the exact waypoint position leading to the horizontal profile being too far out of alignment. There is no way this would have been certified in real life if the INS produced these results so I am wondering whether our INS could be inaccurate compared to the real thing, or is it a limitation of P3D. 

Any ideas? 

Frazz

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This will sound like a very stupid question and sorry if it offends, but are you making sure to put in the coordinates in the right format?

If you put in simple coords from a normal map or google maps or the like it could be the source of one of the problems.

Other than that, this sounds interesting so I will give it a try. I routinely fly these kinds of homebrew INS/Steerpoint approaches in military sims, where homemade instrument approaches are sometimes necessary due to the lack of a functional ILS at the airfield. It works very well as long as you are careful about obstruction clearance along the flight path.

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Robert J Toten

You're talking about an RNAV approach? I have never tried on in the Concorde (or any aircraft in which I have the DelCo Carousel installed). Theoretically, it should be able to do it. It depends if the Concorde + CIVA installation was certified for RNAV instrument approaches (I doubt it). Turn anticipation should be a function of turn angle and ground speed, and the approach will have margins for these turns. What may appear as 'too wide of a turn' may actually be entirely appropriate for the procedure.

It's not enough to ensure the aircraft/INS is certified, you have carefully look at the approach notes to see if DME/DME/IRU is an acceptable system for the approach. Sometimes it will instruct which DME's are required to be used. You're going to get the best results if you comply with all requirements.

My understanding is you're going to input the coordinates which are charted on the approach plate. No guesstimation or conversion should be required.

My understanding is that you shouldn't be in RAD if you're using INS for navigation, your HSI should be displaying INS information for the approach.

Robert Toten.

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If it's recreation of a historical procedure, it'd be interesting to know more about this!

For modern approaches, the laws and regulations I've been able to find states that in almost any country and situation a RNAV based approach or procedure must be selectable from a database where the quality is known (i.e. an FMC) for them to be flown. I haven't found a single case where custom waypoints created along the approach is sufficient for being allowed to fly them under IFR.

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Not only that but the aircraft installation must be approved for RNAV approaches, just having the capable kit is not enough, it has to be Certified for the job.

A paperwork exercise but an expensive one!

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Fabrice Estienne

Hi,

She was BRNAV certified, if I am not mistaken.

BRNAV doesn't suit the PA (Precision Approaches) neither the NPA (Non Precision Approaches).

BRNAV requires DME to fix the bias of the INS.

Concorde is certified for conventional PA and conventional NPA.

Cheers,

Fabrice

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It was a certified procedure and was published in the JFK Airfield book for use. 

I am using the original coordinates from the INS memory segments as were used in 2003.  It is not really about the coordinates being wrong, it's about the INS changing between each one when in "auto" too far out from the waypoint.  Usually you only get down to 0.3 of a mile and it changes. 

If I have time I'll scan the procedure to show you.

Frazz

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Here are the links to the procedure documentation for anyone who wishes to try this.

https://www.dropbox.com/s/g9ljbh03cphbjwk/CRI INS App.jpeg?dl=0

https://www.dropbox.com/s/lkbhs083wf7ebub/Ins Data Mem CRI.jpeg?dl=0

I think the INS memory supplied with Concorde X might have segment 14 already but I'm not sure as I have re-made all of mine to match the real life ones.

I won't answer all the points people have brought up here but just a few comments:

With the INS 1 & 2 in DME update mode from two different VORs the accuracy of the system should be extremely good, even for its age, and because the waypoints were stored and recalled from a built in memory it was working just like the database on an FMGS. This would probably have been what BA would have used to convince the authorities that Concorde was compliant with the regulations. 

The crew must also ensure that the INS has a number 1 as its accuracy number - meaning it is as accurate as it can be - before flying the approach. 

I think we must also remember that the original version of area navigation dates from before flight management computers, with radials from adjacent beacons and LORAN and DECCA versions etc, although I accept that these were basic versions unlike the FMGS of today. 

Enjoy!

Frazz

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