another email virus to watch for

[kinmel]

Register says to watch for Subject: "Here you Go"  or "Here you have"

[Rik]

I think I'm giving up email and going back to morse code. 

[JB]

....  .  .-.  .    -.--  ---  ..-    --.  ---

[Rik]

  I think.

[Ray]

.-.. .. -.- . - .. ... -.-- --- ..- -- . .- -. 

[Baz]

geeks     

[Rik]

You can always tell the former Boy Scouts, can't you.

[Ray]

Not me, Rik, I got it from here 

[Rik]

Looks like you had a sticky key, Ray.

[Ray]

Sausage fingers, I think, Rik,

[Rik]

Who's were they, DR or one of our new companies?

[Ray]

Supreme Sausages, Rik,

[Rik]

 

[JB]

You can always tell the former Boy Scouts, can't you.

I had to learn it for my chosen carear. Not that it's of much use these days with satnav and inertial navigation.

[Rik]

Inertial navigation. Is that getting me to walk in a straight line?

[Glenn]

Inertial navigation, I had weeks on end learning the theory behind it  

[Rik]

Care to do a quick summary?

[JB]

Care to do a quick summary?

How long have you got?

[Rik]

As long as it takes.

[JB]

As long as it takes.

OK. Here's a starter:-

http://www.ehow.com/about_5900085_inertial-navigation-system-theory.html

[cavillas]

...---... I give up, help.

[Rik]

The St Bernards is on the way.

[MisterW]

I had weeks on end learning the theory behind it

Weeks!!, how come. Basically, as long as you know where you started from, you accurately measure acceleration in all three directions,
integrate it a couple of times to get speed and then distance and Robert's your not too distant relative. Simples
Ok, so its not really that simple, you've got to measure acceleration VERY VERY accurately otherwise the drift ( error in distance calculated ) is large.
Most inertial systems need some other form of position input to correct for this drift factor over the long term.

[Rik]

Er, yes.

[Glenn]

Care to do a quick summary?

Here you go, MisterW is asking questions tomorrow http://www.navlab.net/Publications/Introduction_to_Inertial_Navigation.pdf

[MisterW]

Inertial navigation. Is that getting me to walk in a straight line?

No I thought it was trying to get SWMBO to read the map whilst you are driving

[Rik]

Here you go, MisterW is asking questions tomorrow http://www.navlab.net/Publications/Introduction_to_Inertial_Navigation.pdf

[Rik]

No I thought it was trying to get SWMBO to read the map whilst you are driving

[MisterW]

Here you go, MisterW is asking questions tomorrow http://www.navlab.net/Publications/Introduction_to_Inertial_Navigation.pdf

Excellent that Glenn. With all that info I think you should all build a system and Rik can test them out on his visit to Suffolk

[Rik]

I've already checked, we like the look of that place. The menu is very good.

[Glenn]

I've already checked, we like the look of that place. The menu is very good.

[Glenn]

Excellent that Glenn. With all that info I think you should all build a system and Rik can test them out on his visit to Suffolk

I'll get on to it.

[Rik]

http://www.idnetters.co.uk/forums/index.php?topic=21892.msg528625#msg528625

[Glenn]

Ah, I wasn't thinking laterally enough 

[Rik]

 

Check out the menu. I think I'd need three trips at least.

[Glenn]

I've just cancelled my cottage in the Peaks, I'm taking you up on your offer. 

[MisterW]

I've already checked, we like the look of that place. The menu is very good

Only minor issue is that the main building is right on the A140, it used to be a coaching house,
All the rooms, however are in 2 buildings away from the road but if you are a light sleeper then you might get disturbed by the
early morning traffic   

[Rik]

My ears go clothlike.

[JB]

Most inertial systems need some other form of position input to correct for this drift factor over the long term.

This is totally correct. In all modern aircraft the INS is just one tool (input) for updating the actual position over the ground. Data from the INS is compared with GPS data and also positional information calculated from numerous VOR's and TACAN's as the aircraft procedes along it's route. It's all about cross checking as is any element of a flight.

When the automated cross checking fails some form of manual intervention is needed to verify data. These days this is extremely rare.

[Rik]

Do they still carry sextants?

[Glenn]

Nimrods did.

[Rik]

I know they used them in WWII, so I was curious whether that complete manual fallback was still standard practice.

[Glenn]

When I left, the Nimrods were using;

GPS
INS
2 x Gyro magnetic compass
Magnetic compass
Sextant
Moving map projector

The main navigation tool was the INS

[Rik]

And if all that failed, they reverted to an AA road map.

[Glenn]

Not as bizarre as you think, if all else fails, use the mk 1 eyeball

[Rik]

I was being serious, if the were over land at the time. Follow a river or road time...

[Glenn]

It how we got home from Bermuda, the plane was ordered home, with only the standby compass (the magnetic compass) and one gyro compass working. We bumped into Scotland around Glasgow, then followed the A9 north.

I have been to Bermuda twice, the 1st time we were hit by a hurricane, then spent 2 weeks getting the plane fixed, new rudder and control rods for the elevators, plus failing electronics due to the humidity. The 2nd time, after we left, on approach in to the Azores, the plane suffered total power failure for around 15 seconds. Was it the triangle?

[Rik]

You mean you'd had too much Bass to drink?

[Glenn]

Before the hurricane, the flight engineer may have had one or two to many sherbets 

[Rik]

 

[MisterW]

Not as bizarre as you think, if all else fails, use the mk 1 eyeball

When I worked at BAe Woodford on Nimrods, one test flight the Nav system failed totally. They got back by picking up the West Coast mainline,
following it to Crewe and then turning East.

When I left, the Nimrods were using;
GPS
INS
2 x Gyro magnetic compass
Magnetic compass
Sextant
Moving map projector
The main navigation tool was the INS

The early ones I worked on didn't have GPS, but the had the doppler groundspeed and the old 'clockwork' windspeed resolver system. I presume they were dropped when the GPS came in Glenn ?

[Rik]

Probably from a great height.

[Glenn]

Doppler was still in use in 96, the GPS wasn't considered reliable at the time. The Air Data System was still in place too.

[Rik]

Are there any GPS 'not spots'?

[Glenn]

I don't know, but there are INS not spots, the high artic for instance, unless you have special systems.

[Rik]

Life is never simple, eh?

[MisterW]

Doppler was still in use in 96, the GPS wasn't considered reliable at the time. The Air Data System was still in place too.

I left BAe in about 1980, I hate to think that I would have had to work with that ADS for another 16 years or more!

I don't know, but there are INS not spots, the high artic for instance, unless you have special systems.

Didn't the various air forces used to have some sort of competition which involved flying close to ( or over ? ) the pole to see how good their respective Nav systems ( and crews ) were ?

This thread's gone seriously off topic, but never mind.

[Glenn]

We 'borrowed' some 51 sqn INS units, so a plane could meet up with a sub in very high latitudes, as they surfaced through the pack ice.

[Rik]

Did it work, or did they find themselves flying over central London? 

[Glenn]

I believe they were able to get up to around 85 - 87.5 degrees north before gimbal lock, and you don't want that.

[Rik]

I think I may have already had it.

[pctech]

I believe they were able to get up to around 85 - 87.5 degrees north before gimbal lock, and you don't want that.

Sounds painful