GPS users must plan for outages
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Carnal Matey! said
Perhaps you should review these two links:
LINK ONE
LINK TWO
You don't need GPS to use EGPWS. I've flown plenty of aircraft that have EGPWS fitted but not GPS. You just need to make sure you do nav accuracy checks to ensure the FMS/IRS position is within tolerance compared to the raw data position.
LINK ONE
LINK TWO
"I can count on exactly three times when the GPS signal faded or was not available...and never during an approach to GPS minimums"
So, 411A, let's get this right. You have experienced GPS becoming unavailable - so it is NOT 100% reliable. But because it happened not to be at a critical phase of the flight - it's all right then. Aren't you the lucky one! What if it had occured at a critical phase of the flight?
One major problem with GPS is if one satellite begins to transmit rubbish. This can result in incorrect positions being calculated and may take time to be detected and the satellite switched off or the constellation health message upgraded to broadcast this fact.
That's why there are systems like EGNOS which have fixed receivers at known positions constantly monitoring their GPS derived positions and immediately broadcasting notification of GPS unreliability. If GPS was perfect EGNOS (or WAAS and LAAS) would not be needed.
It's not a "not invented here" syndrome in Europe. It is more of a "it WAS invented here" syndrome in the US and therefore it MUST be perfect. Fact is, it isn't! And where lives could be at risk sticking your head in the sand is not a professional approach.
So, 411A, let's get this right. You have experienced GPS becoming unavailable - so it is NOT 100% reliable. But because it happened not to be at a critical phase of the flight - it's all right then. Aren't you the lucky one! What if it had occured at a critical phase of the flight?
One major problem with GPS is if one satellite begins to transmit rubbish. This can result in incorrect positions being calculated and may take time to be detected and the satellite switched off or the constellation health message upgraded to broadcast this fact.
That's why there are systems like EGNOS which have fixed receivers at known positions constantly monitoring their GPS derived positions and immediately broadcasting notification of GPS unreliability. If GPS was perfect EGNOS (or WAAS and LAAS) would not be needed.
It's not a "not invented here" syndrome in Europe. It is more of a "it WAS invented here" syndrome in the US and therefore it MUST be perfect. Fact is, it isn't! And where lives could be at risk sticking your head in the sand is not a professional approach.
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All very elementary
<<So, 411A, let's get this right. You have experienced GPS becoming unavailable - so it is NOT 100% reliable. But because it happened not to be at a critical phase of the flight - it's all right then. Aren't you the lucky one! What if it had occured at a critical phase of the flight?>>
What?
You have never heard of INS becomming unreliable?
I have had two out of three fitted failing more the once certainly, yet we pressed on with the flight, using other modes of navigation.
Just because 'it' might fail enroute, is no reason to get in a panic, now is it?
For approaches, there are VOR's and ILS's available, and indeed the odd diversion might be needed.
All in the name of the game of professional flying.
Now, I can understand why younger guys might have a slight 'problem' but those of us who have been around awhile, manage to cope.
Then we come to map shift on several types just a few short years ago.
Did these guys panic, and have a fit?
I suspect, surely not.
What?
You have never heard of INS becomming unreliable?
I have had two out of three fitted failing more the once certainly, yet we pressed on with the flight, using other modes of navigation.
Just because 'it' might fail enroute, is no reason to get in a panic, now is it?
For approaches, there are VOR's and ILS's available, and indeed the odd diversion might be needed.
All in the name of the game of professional flying.
Now, I can understand why younger guys might have a slight 'problem' but those of us who have been around awhile, manage to cope.
Then we come to map shift on several types just a few short years ago.
Did these guys panic, and have a fit?
I suspect, surely not.
One major problem with GPS is if one satellite begins to transmit rubbish. This can result in incorrect positions being calculated and may take time to be detected and the satellite switched off or the constellation health message upgraded to broadcast this fact.
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First Modernized GPS Satellite Launched
The first modernized GPS satellite meant to provide significantly improved navigation performance for civilian users worldwide, and U.S. military for its special purposes, has been put into orbit.
The satellite is the first in a series of eight GPS IIR-M satellites that will offer a variety of improvements for GPS users' once initial operational capability is reached. This latest series will offer a variety of enhanced features for GPS users, such as a new antenna panel that provides increased signal power to receivers on the ground, two new military signals for improved accuracy, enhanced encryption and anti-jamming capabilities, and a second civil signal that will provide non-military users with an open access signal on a different frequency that should improve its capability for critical navigation purposes.
The current GPS constellation of 28 spacecraft includes 12 fully operational Block IIR satellites, which were previously developed to improve the global coverage and overall performance of the system.
The dash M satellite, built by Lockheed Martin for the U.S. Air Force contingent at the Navstar GPS Joint Program Office, was launched aboard a Delta II rocket on September 25 from Cape Canaveral in Florida. 10-02-2005.
The satellite is the first in a series of eight GPS IIR-M satellites that will offer a variety of improvements for GPS users' once initial operational capability is reached. This latest series will offer a variety of enhanced features for GPS users, such as a new antenna panel that provides increased signal power to receivers on the ground, two new military signals for improved accuracy, enhanced encryption and anti-jamming capabilities, and a second civil signal that will provide non-military users with an open access signal on a different frequency that should improve its capability for critical navigation purposes.
The current GPS constellation of 28 spacecraft includes 12 fully operational Block IIR satellites, which were previously developed to improve the global coverage and overall performance of the system.
The dash M satellite, built by Lockheed Martin for the U.S. Air Force contingent at the Navstar GPS Joint Program Office, was launched aboard a Delta II rocket on September 25 from Cape Canaveral in Florida. 10-02-2005.
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My 2 cents worth....Try using the damm thing in my neck of the woods and you might change your ideas on GPS reliability. We fly GPS NPA into a field with no other aids and have failures on a regular basis, lucky for me the other side kept working, but we do have times when both sides fail, luckily in VMC though. But still my company insists that it's nothing to be worried about, especially the high terrain ....which they say is depicted on the EHSI via the TAAD of EGPWS, .....I guess not. God knows how we got approved to do the approach?
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God knows how we got approved to do the approach?
If that isn't enough and if, as I suspect, you're in Oz and using TSO C129a gear, then you need an alternate that has a serviceable navaid. But then, I'm sure you knew all of that already.
