NTSB: Cockpit weather displays could mislead private pilots

I have not seen these long WX delays with XM except when you loose the signal in the vicinity of GTK or at the fringe of signal coverage. I think these long delays events are more related to the WX receiver not receiving the signal and displaying the old data rather than the NEXRAD WX update. This is a problem that can be more common with ADS-B WX via UAT link than with XM\WX. In either case always look at the data age field. Having an external WX antenna improves the WX updates since there less signal interruption.

Jose
 
You miss the point Jose. At best, Nexrad itself only updates every 6 minutes (precipitation mode; I think there's also a rarely used 5 minute mode). In clear air it's 10 minutes. Your XM weather that was updated 1 minute ago is at least 7-11 minutes old, assuming XM updates it on exactly the same schedule as Nexrad itself. It could be 15-20 minutes old.

The error of thinking that the weather being painted is "real time" (or equal to the time on your screen) and that you can use it for tactical (as opposed to strategic) severe weather navigation is exactly the problem the NTSB is talking about.
 
So I guess now when I say the same thing it won't bring a flame front down on me. I noticed that problem the first time I used it in Bob Geraces 310. We were in a lot of weather crossing TX and the MX-20 was showing > than 20 minutes since last update. We get into a clear spot and it would update then lose it again in the weather. Since then I've watched it show a cell in front of me when I'm looking out the right window at it. This is the same cell that ATC is telling me to turn into as well.

I've always said that this broadcast radar stuff is strictly for strategic decision making.
 
Henning said:
I've always said that this broadcast radar stuff is strictly for strategic decision making.
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:yeahthat:

To put the NTSB report in plain language: Lazy pilots don't take the time to LEARN their systems well enough to know their weaknesses as well as their strengths. For these "pilots" the more gismos you have in the panel the safer you are. Safety is between the ears folks. Everything else is a bonus. Why I heard tell that in 1927 a guy with a chart, a clock and a compass left New York and found Paris all by himself. :dunno:
 
I use it as a strategic tool. For me, the best "value" is in watching it from update to update, seeing where the storms are headed, and refer to my stormscope & eyes for tactical. By watching trends, one can often infer where the storms will be when you get there. It's certainly not real time.

Works quite well when used as one tool in the toolbox. But, a man has to know it's limitations.
 
Henning said:
So I guess now when I say the same thing it won't bring a flame front down on me. I noticed that problem the first time I used it in Bob Geraces 310. We were in a lot of weather crossing TX and the MX-20 was showing > than 20 minutes since last update. We get into a clear spot and it would update then lose it again in the weather. Since then I've watched it show a cell in front of me when I'm looking out the right window at it. This is the same cell that ATC is telling me to turn into as well.

I've always said that this broadcast radar stuff is strictly for strategic decision making.
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Exactly.

Somedays , it is better than others, but it is still a tool. When all else fails look out the window? :rofl:
 
wsuffa said:
By watching trends, one can often infer where the storms will be when you get there. It's certainly not real time.
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And that's the bottom line. For a two or three hour flight, you see the trend. As a long time XM weather user, it works perfectly for that; and beats numerous inflight calls to an FSS. I've found it extremely valuable for mountainous areas of the western U.S.

L.Adamson
 
Henning said:
So I guess now when I say the same thing it won't bring a flame front down on me.
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It shouldn't.

It's a training issue. Unfortunately, like weather itself, weather systems seem to get short shrift during training. And most pilots probably don't get any training at all when adding, say XM weather to an old 396 or a Stratus box to an iPad.

"Nexrad updates where there is no precipitation
a. 1 minute
b. 3 minutes​
..."

would probably be a better private and instrument knowledge test question than the one about applying the 1:60 rule to figure out how far you are from a VOR.
 
I'd agree that questions on Nexrad would be far more pertinent to the private pilot today than questions on VORs and especially NDBs.

As with any tool, knowledge of how to use it is important. Even on-board radar won't help if you don't know how to interpret it.
 
So on Friday - after I was released from the ground hold precipitated in part by the Atlantic City fire and in part due to the TSRA to the west - ATC asked me if I had radar on board and whether I thought LDN-CKB looked OK. His display didn't go out that far.

I thought it looked OK, based on trends, as it turned out once I got on the segment that the buildups were not dissipating as quickly as expected, but that there was a big hole a few miles west of course. Requested and was granted deviations. I was through the line (and knew I would be) in 15 miles, and was able to continue with no problem.

Without the Nexrad (and the trends) I wouldn't have tried. Stormscope alone didn't cut it that day, nor did Nexrad alone.
 
Ted DuPuis said:
Even on-board radar won't help if you don't know how to interpret it.
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On-board radar is probably harder to interpret than Nexrad. You need to be aware of the shadowing effect of attenuation. It's also not as clear that the echoes you are seeing are precipitation. They could be a city or terrain. The big plus is that it is real time.
 
midlifeflyer said:
You miss the point Jose. At best, Nexrad itself only updates every 6 minutes (precipitation mode; I think there's also a rarely used 5 minute mode). In clear air it's 10 minutes. Your XM weather that was updated 1 minute ago is at least 7-11 minutes old, assuming XM updates it on exactly the same schedule as Nexrad itself. It could be 15-20 minutes old.

The error of thinking that the weather being painted is "real time" (or equal to the time on your screen) and that you can use it for tactical (as opposed to strategic) severe weather navigation is exactly the problem the NTSB is talking about.
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Like I said before I have not observed these delays I fly a lot here in Florida around thunderstorm activity and have found XM correlation with small isolated cells to be right on. I use an Aera 560 and the most delay I have seen was for Satellite and that was 7 minutes. In the Bahamas Satellite depiction is right on for what I observe with my eyes. The only time I have seen delays is when the XM antenna is not in full view of the sky that causes the XM receiver to miss WX updates.

BTW if NEXRAD had such long delays then ATC would be giving bad routing around weather to the airlines.

José
 
Piloto said:
BTW if NEXRAD had such long delays then ATC would be giving bad routing around weather to the airlines.
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Airlines have on-board radar and ATC reroutes around weather usually clear it by a large margin. I think part of the reason for big reroutes is that ATC doesn't want a large volume of traffic deviating here and there so instead they take everyone well out of the way.
 
So the NTSB feels the need to issue a warning about the lag time in weather that is patently obvious to anyone who has actually read the manual? Whats next? The NTSB issuing warnings not to run out of fuel?


This gives me pause now about ADS-B TIS - how off is that?
 
Piloto said:
Like I said before I have not observed these delays I fly a lot here in Florida around thunderstorm activity and have found XM correlation with small isolated cells to be right on. I use an Aera 560 and the most delay I have seen was for Satellite and that was 7 minutes. In the Bahamas Satellite depiction is right on for what I observe with my eyes. The only time I have seen delays is when the XM antenna is not in full view of the sky that causes the XM receiver to miss WX updates.

BTW if NEXRAD had such long delays then ATC would be giving bad routing around weather to the airlines.
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Thats generally how it's been for me. Can be off some, but not anything close to 20 minutes as being the standard.
 
Having both on board radar as well as downlinked Nexrad, neither is perfect, as has been stated. However, in addition to being somewhat old, Nexrad can also be inaccurate- over the last month and over 25 hours from South Dakot to Florida on long distance trips, there have been several times when the Nexrad showed areas of precipitation that were completely clear and dry.

Looking out the window is great, except not so useful at night.

Stormscope adds another level of useful information.

None of them alone is perfect, and all require some thought and interpretation.
 
Everskyward said:
Airlines have on-board radar and ATC reroutes around weather usually clear it by a large margin. I think part of the reason for big reroutes is that ATC doesn't want a large volume of traffic deviating here and there so instead they take everyone well out of the way.
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Big reroutes on approach?. Anyone that has done IMC approaches in the vicinity of thunderstorm activity knows that ATC weather advisory is right on with observed weather. ATC can not afford to be in error when guiding traffic around weather on approach. Much less have 20 minutes delays.

José
 
I just provide myself with lots of buffer from anything that could kill me and I haven't scared myself yet.
 
Piloto said:
Like I said before I have not observed these delays I fly a lot here in Florida around thunderstorm activity and have found XM correlation with small isolated cells to be right on. I use an Aera 560 and the most delay I have seen was for Satellite and that was 7 minutes. In the Bahamas Satellite depiction is right on for what I observe with my eyes. The only time I have seen delays is when the XM antenna is not in full view of the sky that causes the XM receiver to miss WX updates.

BTW if NEXRAD had such long delays then ATC would be giving bad routing around weather to the airlines.

José
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I observe it quite frequently. Afternoon cells in FL though are typically stationary so you won't see a difference.
 
There is always a lot of talk about this, especially around false confidence. If a storm is moving at 30 knots and the delay is 6 mins. 1 Knot = 101' a minute or ~3,000' per min at 30 knots. So in 6 mins the storm has moved 18,000'/5240' in a mile = 3.4 miles. If you are going around it to the upwind side round up to 5 miles, plus a standard 20 mile separation, give it 25-30 miles to be safe.

If you're shooting the gap you just have to visually see the storms and then match the pattern up to the XM image.

If IMC match the stormscope up to the XM image to judge the offset. Give the storm even more margin in those situations for higher possible error.

This is no harder than computing a top of descent for a crossing restriction.

Using XM to go inside of 20 miles from convection is just like going visually inside of 20 miles, dangerous, so I don't do it.

Maybe I'm over simplifying, but I really do like XM used conservatively.
 
Piloto said:
Big reroutes on approach?.
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I didn't say anything about approaches, but Denver will often shut down arrival or departure gates when there is any activity in the area. Also, enroute, I have been given reroutes hundreds of miles out of the way for weather.

Piloto said:
Anyone that has done IMC approaches in the vicinity of thunderstorm activity knows that ATC weather advisory is right on with observed weather. ATC can not afford to be in error when guiding traffic around weather on approach. Much less have 20 minutes delays.
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Weather that ATC gives pilots in the terminal area is much better than it was 10 year ago but still not real time. They often ask pilots about the conditions they are observing.
 
Everskyward said:
On-board radar is probably harder to interpret than Nexrad. You need to be aware of the shadowing effect of attenuation. It's also not as clear that the echoes you are seeing are precipitation. They could be a city or terrain. The big plus is that it is real time.
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I'd agree. Plus, I've noticed significant variations in what you see on the display between varying units. The old RCA Primus in the Aztec doesn't work as well as the KWX56 or the RDR-130 in the 310 and Navajo. However, all three of them end up working a bit differently due to their capabilities. So, I have to recalibrate my brain for each one.

Nexrad is nexrad is nexrad, at least from what I've seen.
 
scottd said:
José,

Terminal radars such as the ASR-9 or ASR-11 are actually dual fan beam Doppler radars that also pick up on precipitation. Their display is much better than we'll ever get in the cockpit from that perspective. In addition, some high impact airports have Terminal Doppler Weather Radar (TDWR) located about 7 - 10 miles off the field. These can track gust fronts, wind shear events and microburst in near real time. This is information that can be passed along to the pilots as it happens.
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Most airports with an instrument approach have no ASR-9 or ASR-11 radars. BTW tornadoes are detected by NEXRAD radars and for this you ca not afford a 20 minutes delay.

José
 
Everskyward said:
On-board radar is probably harder to interpret than Nexrad. You need to be aware of the shadowing effect of attenuation. It's also not as clear that the echoes you are seeing are precipitation. They could be a city or terrain. The big plus is that it is real time.
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And if your radar tilt is not gyro stabilized it will show terrain every time you turn or pitch down. True that onboard radar is real time but you have to look a several scans to assess weather movement while with XM/WX there is a vector symbol showing cell motion direction. Not to mention that it is a pain adjusting the radar tilt during turbulence on approach.

José
 
Alexb2000 said:
There is always a lot of talk about this, especially around false confidence. If a storm is moving at 30 knots and the delay is 6 mins. 1 Knot = 101' a minute or ~3,000' per min at 30 knots. So in 6 mins the storm has moved 18,000'/5240' in a mile = 3.4 miles. If you are going around it to the upwind side round up to 5 miles, plus a standard 20 mile separation, give it 25-30 miles to be safe.

If you're shooting the gap you just have to visually see the storms and then match the pattern up to the XM image.

If IMC match the stormscope up to the XM image to judge the offset. Give the storm even more margin in those situations for higher possible error.

This is no harder than computing a top of descent for a crossing restriction.

Using XM to go inside of 20 miles from convection is just like going visually inside of 20 miles, dangerous, so I don't do it.

Maybe I'm over simplifying, but I really do like XM used conservatively.
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What you are failing to factor is that development is dynamic as well, you can't just "line up" a 6 minute old pattern because the entire pattern can be different. Lines don't just move, cells grow and play out in that time as well.
 
Henning said:
What you are failing to factor is that development is dynamic as well, you can't just "line up" a 6 minute old pattern because the entire pattern can be different. Lines don't just move, cells grow and play out in that time as well.
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I gather you are not an XM fan. In six minutes a cell might change, but can you have a cell mostly/fully develop from nothing in 6 minutes? If so what would you do visually under the same scenario assuming you could even see it until it became somewhat developed.
 
Alexb2000 said:
I gather you are not an XM fan. In six minutes a cell might change, but can you have a cell mostly/fully develop from nothing in 6 minutes? If so what would you do visually under the same scenario assuming you could even see it until it became somewhat developed.
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I departed Ft Wayne IN for St Louis one severe clear morning with a briefing of fine clear VFR all day. I was just past Indianapolis when the first cloud developed. Within 5 minutes I was diving through the last hole for the deck (I was a VFR PP in a plane with no nav radios functioning). I finished the flight underneath driving around the dumping cells and following I-70.

What I do is stay visual unless I have onboard radar, I have witnessed what happens in those clouds first hand, I have been in the very worst of it at sea as well. I know well exactly WTF it is I don't want to tangle with and where it lives.
Consider that many people consider me extremely risk tolerant and that I will not risk IMC in T-Storm country without onboard radar, which BTW I know very well how to use and interpret.

4 or years ago coming back to Atlanta from OSH, I was left seat in Leigh Roberts' Travelair and we are penetrating some serious weather over the mountains to the North of Atlanta. I'm skirting around a black assed cloud downwind off my right wing looking at a lightening sky ahead. ATC calls me up and tells me to turn 60* right to avoid a major cell he was painting. Leigh who had been resting his eyelids opens them looking at the 496, "Hey yeah, there's a big cell right there turn right." :nonod::nonod::nonod: "Memphis that's a negative, that cell is off to the west of me in the path you're turning me. I'm visual and looking at clearing skies in 20 miles." At this point Leigh looks out his window an about s-ts his britches and ATC calls a Comanche behind me he had redirected as well and gave him a steer to get behind me.

It has nothing to do with like or dislike, I recognize the limitations of the technology and don't use it to blow smoke up my own ass to make me feel safer operating around weather. I feel perfectly safe operating in weather without XM, I don't mind having it, I don't need it and I surely do not use it as any sort of tactical weather picture. It's just another piece of information, one that is of third tier value, that's it. If you convince yourself it's anything more than that you're setting yourself up for a surprise.
 
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Henning said:
It has nothing to do with like or dislike, I recognize the limitations of the technology and don't use it to blow smoke up my own ass to make me feel safer operating around weather. I feel perfectly safe operating in weather without XM, I don't mind having it, I don't need it and I surely do not use it as any sort of tactical weather picture. It's just another piece of information, one that is of third tier value, that's it. If you convince yourself it's anything more than that you're setting yourself up for a surprise.
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IMO, for me, it's not really a matter of feeling safer. It's a case of making informed inflight decisions, in regards to weather that may still be hundreds of miles ahead. In the mountain west states, this value is highly worth while, and worth the cost. Never the less, I have years of actual experience with XM, and I'd give it a lot more credit, than just a third tier value. I know of many other uses, who would say the same thing.

L.Adamson
 
Friday I was heading north toward 3 Lakes (40D) from Chicago. The convective outlook had talked about a possibility of thunderstorms in the upper midwest, but I hadn't seen anything in the Area Forecast. Approaching Green Bay I was watching this cloud formation ahead of me (I was visual at 3500') and my NEXRAD on the 496 was painting some activity with tops 25000 that I didn't want to mess with. There appeared to be a nice slot between two cells, thgh, and it was confirmed visually. I slowed below Va and headed towards the slot, which showed clear on the other side, both visually and on NEXRAD. I did find the NEXRAD a bit behind realtime, even accounting for the reported delay.

Approaching the slot, I saw some cloud to ground lightning strokes on the west side of the easterly cell. Thanks to the NEXRAD, I had an idea of how far to the west I needed to deviate to go entirely around the cells and, more importantly, knew that once I got past them that there weren't a whole lot more lying in wait for me.

I was cognizant the whole time that there was a lag between what was reported on NEXRAD and what I was seeing outside the window.
 
Henning said:
4 or years ago coming back to Atlanta from OSH, I was left seat in Leigh Roberts' Travelair and we are penetrating some serious weather over the mountains to the North of Atlanta. I'm skirting around a black assed cloud downwind off my right wing looking at a lightening sky ahead. ATC calls me up and tells me to turn 60* right to avoid a major cell he was painting. Leigh who had been resting his eyelids opens them looking at the 496, "Hey yeah, there's a big cell right there turn right." :nonod::nonod::nonod: "Memphis that's a negative, that cell is off to the west of me in the path you're turning me. I'm visual and looking at clearing skies in 20 miles." At this point Leigh looks out his window an about s-ts his britches and ATC calls a Comanche behind me he had redirected as well and gave him a steer to get behind me.

It has nothing to do with like or dislike, I recognize the limitations of the technology and don't use it to blow smoke up my own ass to make me feel safer operating around weather. I feel perfectly safe operating in weather without XM, I don't mind having it, I don't need it and I surely do not use it as any sort of tactical weather picture. It's just another piece of information, one that is of third tier value, that's it. If you convince yourself it's anything more than that you're setting yourself up for a surprise.
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We're kind of mixing apples and oranges. In your example center tried to turn you into a storm. That has nothing to do with XM. Of course both XM and Center's radar painting the same storm that didn't exist seems odd also. Of course it would be great to have an airliners radar, but that isn't realistic or possible for most of us. Some old small dish GA onboard radar has its limitations as well. If your point is VFR is the safest, who couldn't agree with that. At the end of the day we're all just up there doing the best we can with what we've got.
 
L.Adamson said:
IMO, for me, it's not really a matter of feeling safer. It's a case of making informed inflight decisions, in regards to weather that may still be hundreds of miles ahead. In the mountain west states, this value is highly worth while, and worth the cost. Never the less, I have years of actual experience with XM, and I'd give it a lot more credit, than just a third tier value. I know of many other uses, who would say the same thing.

L.Adamson
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That is Strategic decision making, that is what I said it IS good for. If you want to use it to punch blind through convective lines, go for it, but it is no more than third tier information in that regards.
 
Alexb2000 said:
We're kind of mixing apples and oranges. In your example center tried to turn you into a storm. That has nothing to do with XM. Of course both XM and Center's radar painting the same storm that didn't exist seems odd also. Of course it would be great to have an airliners radar, but that isn't realistic or possible for most of us. Some old small dish GA onboard radar has its limitations as well. If your point is VFR is the safest, who couldn't agree with that. At the end of the day we're all just up there doing the best we can with what we've got.
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You don't have to be VFR to stay visual, I do it IFR as well. I have never told ATC 'I need 20 left to avoid some weather' or whatever it was I needed to do to stay visual and had them deny me. They understand full well I want to keep my eye on the weather and give me what I ask. Considering the traffic in the area is low at those times, it's never been a problem. That's why I always carry some extra fuel when flying through weather because I know damn well I won't be flying straight line 'direct'.
 
scottd said:
José,

I was just commenting on your statement about "airliners" getting vectored around weather. That will typically occur in regions or at airports where you have ASR-9/11 radars and TDWR. Actually NEXRAD cannot detect tornadoes directly. They can detect shear or mesoscale circulation based on the velocity component. It is up to the forecaster at the local WFO to issue a tornado warning at that point.
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Map of NEXRAD and TDWR locations:
http://www.wunderground.com/radar/map.asp

Notice that many states like California, Alaska and others have no TDWR, so I guess ATC use NEXRAD for weather advisory.

José
 
Piloto said:
And if your radar tilt is not gyro stabilized it will show terrain every time you turn or pitch down. True that onboard radar is real time but you have to look a several scans to assess weather movement while with XM/WX there is a vector symbol showing cell motion direction. Not to mention that it is a pain adjusting the radar tilt during turbulence on approach.
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The difference is that, if you are using XM to give you information on weather surrounding you on an approach, it better bet to let you know the area is completely clear. XM and real radar are two different tools.

I have seen the delays exist with XM. Sometimes I've not been able to get a new signal for 30 minutes or more. Annoyingly, this has typically been right when I'm near a major cell or line that only a fool would fly through. The on-board radar let me know where I could fly, and I used that. I would never consider using XM for threading needles that closely.

Enough people have gotten themselves in trouble with XM because they trust it too much on precise locations. Those who leave themselves plenty of room and use it for strategic decisions (like "The state of Ohio is one big thunderstorm, I should fly over Kentucky instead") are using it correctly. I do believe, though, that education on these tools should be increased.
 
Henning said:
You don't have to be VFR to stay visual, I do it IFR as well. I have never told ATC 'I need 20 left to avoid some weather' or whatever it was I needed to do to stay visual and had them deny me. They understand full well I want to keep my eye on the weather and give me what I ask. Considering the traffic in the area is low at those times, it's never been a problem. That's why I always carry some extra fuel when flying through weather because I know damn well I won't be flying straight line 'direct'.
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I just left KMEM a couple of weeks ago. I went into the clag immediately on the climb out and there was not one break until I was at 14K. The sky was SOLID overcast with light rain in every direction for 200 NM. The point is there are circumstances where even a pilot that likes to remain visual is going IMC if they fly IFR. In those cases the tools are great to have vs. nothing.

What do you do on those days?
 
scottd said:
José,

Yes, I'm very familiar with the NEXRAD and TDWR (I helped develop the software for the TDWR years ago). But, all of the major terminal areas where airliners fly have TDWR and many more have ASR-9 or ASR-11 dual fan beam Doppler radars which depict weather in addition to tracking airplanes. At some of the lower impact Class C airports, they have other weather systems (called Weather Systems Processor or WSP) that provide data to controllers based on the ASR-9 and ASR-11 weather channel that is very similar to the weather info received from the TDWR. This information is much more timely than NEXRAD. ASR-9/11 updates every 30 seconds on the controller's display.

California and Alaska don't have as much of a need for TDWR given the lack of convection based on climatology. Certainly, adverse weather like tornadoes, gust fronts and microbursts are minimal threats on average. They can use the weather data from the ASR-9 or 11s to help airliners get around any significant weather.
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According to the radar map, I guess LAX and ATL do not count as major airline hubs. Oh well that's all you you get with current budget.

José
 
Alexb2000 said:
I just left KMEM a couple of weeks ago. I went into the clag immediately on the climb out and there was not one break until I was at 14K. The sky was SOLID overcast with light rain in every direction for 200 NM. The point is there are circumstances where even a pilot that likes to remain visual is going IMC if they fly IFR. In those cases the tools are great to have vs. nothing.

What do you do on those days?
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If it's convective, I stay on the ground. If it's not, then I launch.
 
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