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Trimeresurus
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Navigation in an old six-pack airliner

Fri Sep 25, 2020 3:13 pm

In the old days, like in 1970 when the first 747s started their Transatlantic flights for Pan Am, how was the main method of navigation? Was it primarily using ground beacons with the CDI and then heading vectors from ATC at lower altitudes/approaches? What about Transalantic routes, which is out of range of any VOR/NDB and ATC radar? I know the these aircraft were equipped with INS, but could you for example, type specific coordinates into the INS and make the aircraft fly into it with at least minimal deviation? Or was that too GPSlike and futuristic for the time? I know these aircraft didn't yet have a LNAV mode so every new leg of the route must have been located every time and adjusted.
 
GalaxyFlyer
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 3:23 pm

Yup, VOR to VOR, set the inbound and outbound courses of the airway/Jet route off the paper charts. The 747 pretty much introduced 10 waypoint INS which produced track and distance plus attitude and speed from the platform. Pilots entered the Lat/Long coordinates and the system did the computations. Autopilots could track the routes from the INS and fly it precisely, but autopilots did a less smooth job on radio navigation.

LNAV is lateral navigation, but relies on databases to store and present routes from the FMS. In the “old” days, pilots used the charts as databases were in the future—early 1980s.
 
Bellerophon
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 6:51 pm

The Carousel IV INS sets (developed and adapted from the INS set used on the Apollo moon missions) were, I believe, first used in civil aviation by Pan Am in 1969, and had to meet the following FAA requirements for accuracy before Pan Am (and later BOAC, along with other airlines) were allowed to dispense with specialist navigators.

95% of all flights had to be within +/- 20 miles cross-track, and +/- 25 miles along track, at destination.

These requirements might seem amazingly lax to us now, but in the early 1960s they were thought very demanding.

This was an era when, on a bad day - perhaps due to prolonged flight in cloud, rain, ice or turbulence, and using forecast winds noticeably less accurate than today - navigators on long ocean crossings who had to rely solely on astro-nav and forecast winds could occasionally, at the other side of the ocean, end up so far away from their planned "Coast-In" VOR or NDB as to be unable to receive it!

In practice, the Carousel IV INS sets met the FAA requirements with ease, generally managing +/- 1 mile drift per hour of flight, something that appeared quite amazing at the time, and navigators disappeared from most, but not all, flight decks fairly swiftly thereafter.
 
SRQfoxtrot
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 7:49 pm

What's a "six-pac" airliner?
 
e38
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 7:59 pm

Quoting SRQfoxtrot (Reply # 4), "What's a "six-pac" airliner?"

Reference to aircraft with "round dials" in the flight deck; generally analog technology. Take a look at a photo of an older airliner; in particular the center display with regard to the engine instruments--looks like a six pack.

e38
 
GalaxyFlyer
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 8:14 pm

SRQfoxtrot wrote:
What's a "six-pac" airliner?


The freighters that hauled Coors beer when the Bandit and Snowman couldn’t.
 
VMCA787
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 8:26 pm

Bellerophon wrote:
In practice, the Carousel IV INS sets met the FAA requirements with ease, generally managing +/- 1 mile drift per hour of flight, something that appeared quite amazing at the time, and navigators disappeared from most, but not all, flight decks fairly swiftly thereafter.



The tolerance for a write-up on the Delco INS was 3+3T where T is the time the INS has been in NAV. I can't remember if that was the tolerance for the FAA or was it the maintenance tolerance. What was really interesting was when you had the INS in Triple Mix, the INS units would vote on what IS information to use. So, you could have one INS unit way out but the other two would do a pretty good job of navigating accurately.
 
thepinkmachine
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 8:41 pm

VMCA787 wrote:
What was really interesting was when you had the INS in Triple Mix, the INS units would vote on what IS information to use. So, you could have one INS unit way out but the other two would do a pretty good job of navigating accurately.


It is still the case on modern triple-IRS setups, eg A320. A330. The 787 is an exception, as it has 2XIRS plus 2X AHRS
"Tell my wife I am trawling Atlantis - and I still have my hands on the wheel…"
 
GalaxyFlyer
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Re: Navigation in an old six-pack airliner

Fri Sep 25, 2020 9:44 pm

VMCA787 wrote:
Bellerophon wrote:
In practice, the Carousel IV INS sets met the FAA requirements with ease, generally managing +/- 1 mile drift per hour of flight, something that appeared quite amazing at the time, and navigators disappeared from most, but not all, flight decks fairly swiftly thereafter.



The tolerance for a write-up on the Delco INS was 3+3T where T is the time the INS has been in NAV. I can't remember if that was the tolerance for the FAA or was it the maintenance tolerance. What was really interesting was when you had the INS in Triple Mix, the INS units would vote on what IS information to use. So, you could have one INS unit way out but the other two would do a pretty good job of navigating accurately.


IIRC, that is the maintenance tolerance
 
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Starlionblue
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 12:32 am

Back in the 747 Classic days, on a flight beyond range of radio becons, position would be kept by INS, which drifts slowly. Once you got close to land on a transatlantic flight, the VOR/DME triangulation would tune the beacons and update the position. So at a certain point the aircraft would go into a turn to adjust its position. IIRC from hearing stories this would be on the order of 5-10 correction.

Nowadays navigation is almost too precise, as you end up in the wake of preceding aircraft. Offsetting for wake turbulence is not uncommon.

Another way of correcting INS was via celestial navigation. This is the reason the VC-10 and 747 Classic had a sextant port in the cockpit ceiling.

Image



SRQfoxtrot wrote:
What's a "six-pac" airliner?


As mentioned above, the six-pack refers to the six main instruments centered on the ADI. This is a Cessna obviously but I thought it was a good illustration.
Image
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
GalaxyFlyer
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 12:51 am

Starlionblue wrote:
Back in the 747 Classic days, on a flight beyond range of radio becons, position would be kept by INS, which drifts slowly. Once you got close to land on a transatlantic flight, the VOR/DME triangulation would tune the beacons and update the position. So at a certain point the aircraft would go into a turn to adjust its position. IIRC from hearing stories this would be on the order of 5-10 correction.

Nowadays navigation is almost too precise, as you end up in the wake of preceding aircraft. Offsetting for wake turbulence is not uncommon.

Another way of correcting INS was via celestial navigation. This is the reason the VC-10 and 747 Classic had a sextant port in the cockpit ceiling.

Image



SRQfoxtrot wrote:
What's a "six-pac" airliner?


As mentioned above, the six-pack refers to the six main instruments centered on the ADI. This is a Cessna obviously but I thought it was a good illustration.
Image


TACAN (really DME) updating was used in the C-5 Delco installation. We had to load the TACAN position, then make a selection in the same position as putting the three units into triple mix and it’d update. Yes, there’s be slow adjustment turn as INS computed position was updated. The ideal geometry was a station off each wingtip, say Goose and St. Anthony coming off the ocean.
 
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zeke
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 5:53 am

Bellerophon wrote:
.


Reference your previous type, did that have INS/IRS or GPS ?
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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747classic
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 9:44 am

After some searching i found my legacy "Pilots Guide Delco Caroussel IV " for our 747-206B aircraft.:

Regarding checking/updating the INS position(s) ovhd radio facility (no auto updating), after crossing the ocean :

- APFD nav mode selector : out of INS
- close to facility : data selector of each INS to "POS"
- Press "REMOTE" on each INS
- When ovhd facility : press "HOLD" and compare positions of INS1,2 and 3 with position of radio facility.
- press "REMOTE" on each INS and then "HOLD" of INS(s) not requiring updating, lights to go out.

On INS, requiring an update :
load correct latitude and press "INSERT"
load correct longitude and press "INSERT"
Check : All lights out.
Check for correct loaded coordinates.
Press "HOLD" , all lights to go out = forced update of relevant INS.


Image
Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
Bellerophon
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 11:20 am

zeke

... Reference your previous type, did that have INS/IRS or GPS ? ...

Triple INS, updated by DME, with the CDU identical to the one pictured above.

We could quickly load a portion of any likely route - called a flight plan segment - by keying in the Flight Plan Segment number, which saved us from manually having to load nine waypoints in each INS set. This facility was particularly useful in the event of a re-route (didn't happen often) as one could travel quite some a distance by the time one had finished loading new waypoints manually!

We also loaded a DME Catalogue number, so the INS "knew" which DME stations to "expect" to use for updating, and all this data was to be found on our flight logs.

Those pilots, like me, coming from the B747 or DC10, found the INS procedures very familiar.

Those coming from a modern two-crew aircraft with FMS could find the lack of a pink string to follow a little disconcerting at first :eek: but all adapted quickly to our old-fashioned ways.

Getting used to the helpful advice and tactful comments our Flight Engineers could offer was sometimes a bigger shock :lol:

Best Regards

Bellerophon
 
VSMUT
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 11:44 am

Starlionblue wrote:
Another way of correcting INS was via celestial navigation. This is the reason the VC-10 and 747 Classic had a sextant port in the cockpit ceiling.

Image


Wow, I've been told about it so many times. I even had to do some basic celestial navigation training when I did my ATPL ground training, but that's the first time I've ever seen a photo of how it was mounted.
 
Gr8Circle
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 2:23 pm

Starlionblue wrote:
Another way of correcting INS was via celestial navigation. This is the reason the VC-10 and 747 Classic had a sextant port in the cockpit ceiling.


The Boeing 707 also had this......probably the DC-8s too....
 
Crackshot
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 3:57 pm

The ALM DC-9 that ditched in the Caribbean in 1970 had a navigator; mind you, it was an overwater flight in an aircraft that only had radio navigation.

The infamous Korean Air shootdown near Sakhalin in 1983 was a result of the aircraft drifting off course because the flight crew either neglected to switch the autopilot navigation source from heading to INS, or they waited too long after departure and it was too late to capture the INS, so instead remained on heading mode.
 
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747classic
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Re: Navigation in an old six-pack airliner

Sat Sep 26, 2020 5:06 pm

Starlionblue wrote:
Back in the 747 Classic days, on a flight beyond range of radio becons, position would be kept by INS, which drifts slowly. Once you got close to land on a transatlantic flight, the VOR/DME triangulation would tune the beacons and update the position. So at a certain point the aircraft would go into a turn to adjust its position. IIRC from hearing stories this would be on the order of 5-10 correction.

Nowadays navigation is almost too precise, as you end up in the wake of preceding aircraft. Offsetting for wake turbulence is not uncommon.

Another way of correcting INS was via celestial navigation. This is the reason the VC-10 and 747 Classic had a sextant port in the cockpit ceiling.

Image



SRQfoxtrot wrote:
What's a "six-pac" airliner?


As mentioned above, the six-pack refers to the six main instruments centered on the ADI. This is a Cessna obviously but I thought it was a good illustration.
Image


AFAIK no celestial navigation updates were ever performed during airline operation of the 747 classics.
On the early VC-10's celestial navigation was used for back up of the Long Radio Navigation aids (Doppler Radar and Loran).
See : https://www.vc10.net/Memories/radio_development.html
Later INS was installed, without celestial back up..
The picture is from an early BOAC VC-10, without INS.
Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
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zeke
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Re: Navigation in an old six-pack airliner

Sun Sep 27, 2020 1:37 pm

Bellerophon wrote:
We could quickly load a portion of any likely route - called a flight plan segment - by keying in the Flight Plan Segment number, which saved us from manually having to load nine waypoints in each INS set. This facility was particularly useful in the event of a re-route (didn't happen often) as one could travel quite some a distance by the time one had finished loading new waypoints manually!


Would they use these for SIDs and STARS ?

I remember the litton LTN-72 on the 74 classic, think it had a memory for 15 waypoints.

Bellerophon wrote:
We also loaded a DME Catalogue number, so the INS "knew" which DME stations to "expect" to use for updating, and all this data was to be found on our flight logs.


It was a very advanced aircraft for its time, first FBW airliner. Would have given my first and second born, and both ex wives to fly it. The idea of doing Mach 2 at FL600 still appeals to me.


Bellerophon wrote:
Those coming from a modern two-crew aircraft with FMS could find the lack of a pink string to follow a little disconcerting at first :eek: but all adapted quickly to our old-fashioned ways.


The magenta line I thought was the entrails of whatever insect or bird one collects on the takeoff roll ;)

Bellerophon wrote:
Getting used to the helpful advice and tactful comments our Flight Engineers could offer was sometimes a bigger shock :lol:


The social directors !!!
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
Crackshot
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Re: Navigation in an old six-pack airliner

Sun Sep 27, 2020 1:53 pm

zeke wrote:
Would they use these for SIDs and STARS ?

I remember the litton LTN-72 on the 74 classic, think it had a memory for 15 waypoints.


I think most SIDs/STARS back in the day were VOR/NDB based. They'd have to be no, for aircraft like the 727/737 classic, DC-9 etc without INS navigation?
 
Max Q
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Re: Navigation in an old six-pack airliner

Sun Sep 27, 2020 4:03 pm

Crackshot wrote:
zeke wrote:
Would they use these for SIDs and STARS ?

I remember the litton LTN-72 on the 74 classic, think it had a memory for 15 waypoints.


I think most SIDs/STARS back in the day were VOR/NDB based. They'd have to be no, for aircraft like the 727/737 classic, DC-9 etc without INS navigation?




That doesn’t preclude aircraft from navigating them with an onboard LNAV system


Would these first generation INS units allow for this and were they used in that manner ?
The best contribution to safety is a competent Pilot.


GGg
 
VMCA787
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Re: Navigation in an old six-pack airliner

Sun Sep 27, 2020 5:57 pm

To be honest, the STARS/SIDS were not built to the same intricate degree as they are now. You could actually insert the SID waypoints or STAR waypoints into the INS. Generally, there weren't as numerous as you would have in the current generation of Nav procedures. The problem with the Delco Carousel was it only held 9 waypoints and you certainly didn't want to be inserting more waypoints in the middle fo the SID. Quite a few times the departure or arrival procedure was very simple so you could just fly it the old fashion way so you would intercept a radial until you intercepted another radial. So, it wasn't a terrible thing to have to do.
 
Max Q
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Re: Navigation in an old six-pack airliner

Sun Sep 27, 2020 7:55 pm

VMCA787 wrote:
To be honest, the STARS/SIDS were not built to the same intricate degree as they are now. You could actually insert the SID waypoints or STAR waypoints into the INS. Generally, there weren't as numerous as you would have in the current generation of Nav procedures. The problem with the Delco Carousel was it only held 9 waypoints and you certainly didn't want to be inserting more waypoints in the middle fo the SID. Quite a few times the departure or arrival procedure was very simple so you could just fly it the old fashion way so you would intercept a radial until you intercepted another radial. So, it wasn't a terrible thing to have to do.





That’s understood, and it was normal to have to add waypoints on longer flights as these early units could only retain nine (if you didn’t do that it would return you to the first one after passing #9)


Of course it’s often simpler and more straightforward to intercept and track a VOR radial


Question is, were these early systems sufficiently accurate and / or certified to fly a SID or STAR ?
The best contribution to safety is a competent Pilot.


GGg
 
Crackshot
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Re: Navigation in an old six-pack airliner

Sun Sep 27, 2020 10:55 pm

Max Q wrote:
Question is, were these early systems sufficiently accurate and / or certified to fly a SID or STAR ?


My guess it would depend on the SID/STAR. For example, look at this departure for MEL.

https://www.airservicesaustralia.com/aip/current/dap/MMLDP04-161_13AUG2020.pdf

Even though it's RNAV, I think that would probably be fine in an INS, IMO. At most there's six waypoints (departing from 34), and the other two runways have two, and it's a straightforward departure with no dramatic twists and turns.
 
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zeke
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Re: Navigation in an old six-pack airliner

Mon Sep 28, 2020 12:32 am

Crackshot wrote:
Even though it's RNAV, I think that would probably be fine in an INS, IMO. At most there's six waypoints (departing from 34), and the other two runways have two, and it's a straightforward departure with no dramatic twists and turns.


RNAV has been around since the 1960s, it has nothing to do with GPS. Before GPS , airliners used to navigate by RNAV using DME/DME/IRS, INU, or even Omega equipped. Is was not uncommon to see a “map shift” after a long time without a ground based update when becoming in range of ground equipment.

Early aircraft did not have a large database onboard like with see in today’s airliners talking to the RNAV equipment automatically to sequence waypoints, we had to enter the waypoints manually. I’m pretty sure tye 74 classic had a memory for 15 waypoints.

The difference today is that some SIDs and STARs can specify a RNAV requirement which are not achievable by the older equipment.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
VMCA787
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Re: Navigation in an old six-pack airliner

Mon Sep 28, 2020 4:54 am

Max Q wrote:

Question is, were these early systems sufficiently accurate and / or certified to fly a SID or STAR ?


The problem with the old INS only systems is the performance varied based on the length of flight. On a SID, I would have no problem flying in on the INS as the system should be fairly tight. Flying an arrival constructed with today's tolerance, that would be another story. But, remember the INS system did meet the MNPS for the time, but it wouldn't meet that standard now. Our SOP on the Delco was never put an update in as experience had shown the system didn't like updates and if you had a weak INS, that INS normally took the update and ran with it to the point where it was useless. At least it was close before the "update".
 
GalaxyFlyer
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Re: Navigation in an old six-pack airliner

Mon Sep 28, 2020 12:49 pm

Are you sure INS didn’t meet MNPS, as INS was pretty much the only nav system until FMS with various sensors (DME/DME, IRS and finally GPS) was introduced
 
VMCA787
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Re: Navigation in an old six-pack airliner

Mon Sep 28, 2020 5:21 pm

INS met the MNPS at the time. However, it wouldn't meet the MNPS today for an RNAV SID/ARRIVAL.

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