GPS jamming becoming a real problem - Page 4 - Airline Pilot Central Forums

#31

captjns , 04-30-2019 04:29 AM

Gets Weekends Off

Quote:

Originally Posted by aviatorhi

Clearly this has never happened to you... while it happens about once every month or two to me.

Rapidly is subjective, but in the span of a few minutes you'll be at a few miles when on inertial only.

GPS jamming NOTAMS, alerts issued by the FAA. GPS anomaly? Yeah consistently near an intersection over the Italian/Swiss boarder. Got they typical RNP message in the FMC/CDU. Came back to life before I had the chance to cancel the message.

Operated across the Pacific with IRS’s. Average leg was 10 hours plus. Required to log velocities and distance errors 10 minutes after the parking brake was set. Trying to remember the greatest distance error was about 2 miles. That said No biggy, unless you need to accomplish a LPV approach.

#32

BobZ , 04-30-2019 08:18 AM

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Excess iru drift is still tabulated i believe.

#33

PurpleToolBox , 05-03-2019 04:17 PM

Gets Weekends Off

Quote:

Originally Posted by captjns

Operated across the Pacific with IRS’s. Average leg was 10 hours plus. Required to log velocities and distance errors 10 minutes after the parking brake was set. Trying to remember the greatest distance error was about 2 miles. That said No biggy, unless you need to accomplish a LPV approach.

And now we have tighter airspace and stricter required navigational performance requirements.

#34

aviatorhi , 06-14-2019 05:09 PM

Banned

Quote:

Originally Posted by JohnBurke

Fly better equipment, or learn to properly initialize before you leave the gate.

Good idea.... but since I already do that do you mind telling the Syrians and Russians to stop jamming the GPS on the Turkey/Iraq border as well? Smartass.

Quote:

Originally Posted by rickair7777

It might raise relatively rapidly immediately following GPS loss, but it should quickly settle down at a reasonable (for non-GPS RNAV) value.

If you're oceanic, on INS only, then ANP should very gradually increase over time without GPS. Same for a hypothetical total jamming of all sat and ground based nav over land.

Look, these are relative concepts... what is rapidly to me might not be the same to you. Typically in a remote area (without ground based NAV) it rapidly gets to about 3-4 NM and then the rate slows down tremendously.

Quote:

Originally Posted by rickair7777

Most of the airplanes we fly used to do RNAV all day long without GPS, and many of them did oceanic with INS only a few decades ago. It shouldn't all just go to poop if you lose GPS.

Yeah, but this isn't 1998, some of the ways ANP is being calculated and implemented (as well as the software) have changed since then. I sure how you wouldn't consider ANP values in the 3-4 range as acceptable for any kind of RNAV based approach in 2019.

#35

JohnBurke , 06-15-2019 02:09 AM

Disinterested Third Party

Quote:

Originally Posted by aviatorhi

Smartass.

Ah, an intellectual.

Quote:

Originally Posted by aviatorhi

Good idea.... but since I already do that do you mind telling the Syrians and Russians to stop jamming the GPS on the Turkey/Iraq border as well?

You tell them. It's a combat zone. Go figure.

If you're already flying better equipment, then it's not really an issue, is it?

#36

ShyGuy , 06-15-2019 10:20 AM

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Quote:

Originally Posted by JohnBurke

It's a bit like not verifying the fuel upload. I see most look at the fuel indication and if it matches what's wanted, the crew is happy. It seems to be a lost basic that one should look at the previous ending fuel, fuel upload, add them and note any discrepancy that isn't explained by APU burn, etc. Simply things, but important, and should be done every time.

Assuming one has an ability to do that. When I walk on the plane and it's already fueling, I have no way to know what the previous flight's remaining fuel was. If I get on the plane and it hasn't fueled yet, I can see the current FOB is the previous flight arrival fuel. However, after my fueling is done I don't know how many gallons are added. The electronic fuel slip delivered on ACARS only shows the paperwork required FOB.

Before the merger, our own airline delivered fuel slips that showed previous arrival fuel and gallons added and I would do that math just like you said to verify it. It was actually part of the our procedures. Not anymore. I don't see how that can be done now, we just don't get that info anymore. SOPs call to 'only' verify the FOB on the screen.

Quote:
As for jamming issues: while there may come a time when ground based navaids or gone, that time is not today. I've never been an advocate of an all-eggs-in-one-basket approach, and am not today. There are locations, of course, that rely only on RNAV and GPS for approaches, arrivals, departures, etc, but when operating IFR to such locations, good airmanship dictates having options that do use ground based navaids, including alternates in mind. It's been mentioned that these concerns are chiefly for general aviation aircraft. Again, good airmanship dictates having a plan B.

It's possible to paint one's self into a box. Don't do that.

I also fly general aviation, sometimes in aircraft with no nav systems; it's either charts or a handheld GPS (and charts); with loss of GPS, then it's pilotage and dead reckoning.

The latter two still work. If one insists on going IFR, and has only RNAV capability, then we're back to good airmanship, which means having a plan to get to VMC and to fly visually.

Well stated

#37

727C47 , 06-16-2019 03:01 AM

Gets Weekends Off

Quote:

Originally Posted by JohnBurke

There is absolutely no justification for initializing the IRU without verifying current position. Doing otherwise is poor airmanship.

One should verify what the former residual IRU performance was, if available, before bringing the system up, however, to get an idea of which unit might be the most efficient in the event of a fail down and a need to rely on one without other nav input. Again, just good airmanship to now which unit shows the strongest and most accurate, before starting the flight. I very seldom see anybody do this.

It's a bit like not verifying the fuel upload. I see most look at the fuel indication and if it matches what's wanted, the crew is happy. It seems to be a lost basic that one should look at the previous ending fuel, fuel upload, add them and note any discrepancy that isn't explained by APU burn, etc. Simply things, but important, and should be done every time.

As for jamming issues: while there may come a time when ground based navaids or gone, that time is not today. I've never been an advocate of an all-eggs-in-one-basket approach, and am not today. There are locations, of course, that rely only on RNAV and GPS for approaches, arrivals, departures, etc, but when operating IFR to such locations, good airmanship dictates having options that do use ground based navaids, including alternates in mind. It's been mentioned that these concerns are chiefly for general aviation aircraft. Again, good airmanship dictates having a plan B.

It's possible to paint one's self into a box. Don't do that.

I also fly general aviation, sometimes in aircraft with no nav systems; it's either charts or a handheld GPS (and charts); with loss of GPS, then it's pilotage and dead reckoning.

The latter two still work. If one insists on going IFR, and has only RNAV capability, then we're back to good airmanship, which means having a plan to get to VMC and to fly visually.

John, God bless that, I used to fly a Champ with just a whiskey compass and a sectional, GPS was cheating, good on you