Delay in sending Spidertracks emergency message

[Dick Smith]

I have been trying to find out the worst case scenario of the time taken after pushing the SOS button on Spidertracks until the satellite actually receives the message.

I did a test recently which I arranged with the recipients of the message. I pushed the Spidertracks SOS button and then waited for at least two minutes before I turned the aircraft battery switch off. I was in a very good location with clear access to 360 degrees of sky, however the message was not sent.

I have had great difficulty in finding out the worst case scenario of the time frame until the message is received by the satellite. I think everyone understands that when using Iridium for messaging there can sometimes be a delay in that message being received.

I am not concerned about the time from when the message has been received by the satellite and there is a delay in distributing that message via service providers. I don’t think that is a problem, but it certainly is a problem if you have an engine failure when flying at 500 ft AGL, push the Spidertracks SOS button, and just as you are about to hit the ground you turn off the battery switch – as you would if prudent.

Does this mean that in some cases the message won’t go through at all? Can anyone help me with this information?

[Hasherucf]

Contact the manufacturer ?

[Dick Smith]

I have but can't get a clear answer!

Someone once told me that the worst case normal situation can be up to 5 minutes.

If so it should be out in the open as a serious potential safety issue.

[Sunfish]

The 66 satellite system is cross linked and requires very fancy routing. That means message storage somewhere and delays - beyond my pay grade to understand.

https://www.agi.com/downloads/corporate/partners/edu/paper_AIAA.doc

Anyway, I dislike spiders.

[Aussie Bob]

The problem with technology is that the better it gets the more we complain about its shortcomings. Who ever would have even thought about Spidertracks a decade ago? Now its not good enough? My thought is that if you need Spidertracks with perfect functionality to feel safe, you may be better off taking up golf.

[Dick Smith]

No. Just want to know what the design parameters are .

Then I will know what I can rely on and what I can't rely on. Pretty straightfoward I would reckon. I bet iridium publish the real details somewhere. Bet there is likely to be someone who reads this site who may have the accurate answer!

[donpizmeov]

There was some discussion before about this by some rotarheads. Did a search but didn't find it. Seems very reasonable to want to understand how ya systems work.

[27/09]

Have you looked at Spot Tracker? It also has an SOS function.

[Dick Smith]

Yes. And if it uses iridium what is the maximum delay while waiting for other messages?

[Derfred]

Spot does not use Iridium. It uses an undisclosed "commercial satellite network". Coverage map is here (http://au.findmespot.com/en/index.php?cid=108). Apparently maximum delay 20 mins (96% chance), unless you go to remote parts of the world.

But it's a fraction of the price, and it has a battery - which resolves the opening query. It also makes it multipurpose - can use for hiking, boating, 4WDing etc.

Oh, and AussieBob, Spot has been around for at least 10 years I'm sure. I was certainly using one in remote Australia nearly 10 years ago. It worked very well then, can't speak for now but if they're still in business I guess it does.

The advantage over an ELB is you can arrange your own SAR for non-urgent situations: HELP vs SOS = "Flat tyre, pls send beer" vs "I've crashed and broken both legs".

[Dick Smith]

A maximum delay of 20 minutes is good to know. What about the 4% remaining? Could it be 39 minutes?

Spider tracks are connected to the aircraft battery so it's important to know what the maximum delay can be.

Very hard to find out. Wonder why?

[Bushfiva]

Spot is Globalstar. The completion rate is defined as an RTU transmitting a single packet message plus two repeats.

[Derfred]

What about the 4% remaining?

Good question. Reminds me of when my aircraft tells me it's position is accurate within 0.2NM it's apparently actually only a 95% probability of being accurate within 0.2NM. So how inaccurate is it the other 5% of the time? 0.4NM? 4NM? 40NM? No-one knows. Or seems to care.

But in actual fact, from experience, it's accurate within 0.02NM at least 99% of the time. I guess that's why no-one cares.

So I'm guessing Spot is much quicker than 20 mins in practice.

[Bushfiva]

The Globalstar data is statistical. Using the Globalstar worst value (90%-100%), (and I'd like to see the math behind it and Spot's figure), if you re-send the message, that (plus two resends) also has a 90% chance of completion, so for two messages there's a 99% chance of completion.

I've no idea how often the Spidertracker stuff repeats once its button is pressed.

Globalstar constellation is in LEO, and voice signals are typically picked up by more than one satellite that has its antenna pointed to the service area. So I'd imagine conditions change moment by moment, as with GPS.

So how inaccurate is it the other 5% of the time?

Surely your GPS can tell you that? Mine all have CEP available.

[Dick Smith]

What I am on about is the confidence factor that you know an emergency message has got through.

Does anyone know if the spidertracks message is sent just once , or a number of times. I suspect just once.

At least if you call mayday on 121.5 and you are answered you know the message has got through.

In some cases the spider track message may not get through if you are forced down and need to turn off the dc supply for safety reasons .

[TWT]

Maybe you could try asking here Dick :

http://www.pprune.org/rotorheads/563527-gps-tracking.html

[Bushfiva]

I guess you could add yourself as one of the emergency contacts if you wanted 100% proof of delivery. The manual also says that the only way to stop it sending an emergency signal is by cycling the power. Or you could just phone the guys: they're generally helpful.

[compressor stall]

In some cases the spider track message may not get through if you are forced down and need to turn off the dc supply for safety reasons .

Which is why a tracker that can be activated independently of the aircraft system would be better (e.g. Spot for populous area use, or YellowBrick Iridium if you are going to far flung corners of the planet ). Also, at least it is in the liferaft with you not at the bottom of the water. There are pros and cons of every system.

[catseye]

There is a secondary position effect when running at 2 minute reporting interval. you should be within about 4-5 miles of the last known position at most helicopter speeds vis about 2 miles per minute. far better chance of having a know search start point. :ok:


does this tracking method work? absolutely and proven. Have it hard wired so when ever the master ( not avionics master ) is powered you know exactly where the machine is.

[BuzzBox]

In some cases the spider track message may not get through if you are forced down and need to turn off the dc supply for safety reasons .

My understanding is that Spidertrack has a 'Watch' mode where the ground system automatically monitors the flight. If no position reports are received over a 10 minute period, the ground system automatically notifies the user's SOS contacts. Does that not cater for the case where the aircraft battery must be turned off for some reason?

[Dick Smith]

I am not asking about watch mode. I understand how that works.

Surely iridium must publish a worst case delay time for an emergency text message to be received by their sattelite . Is it seconds or minutes?

[BuzzBox]

I understand what you are asking, but you have stated several times that you are concerned that your SOS contacts won't be notified if the aircraft battery is turned off after an SOS is sent. In that event, the Watch mode will still notify your SOS contacts after a 10 minute time delay, so what's the big concern?

[STL]

Great questions. I'll attempt to clarify some of this. The Iridium network is fairly dynamic - delays of up to 5 mins can happen within the bounds of "normal variability" however the 95th percentile is less than 30 seconds. If you see a delay of several minutes once there may not be any issue, if it is happening frequently then there could be some localised issue, either within the operating environment or with the device itself. Our support will be able to get a beat on that for you very quickly. If you are flying remotely, it is a good idea to use 'Watch'. This is an active tracking mode whereby the Spidertracks system monitors the status of your flight through to conclusion. If contact is lost with the aircraft during flight a notification is sent out through your emergency management network (which you have pre configured), along with a 4-dimension vector of your position. This is a paradigm shift from the ELT type of thinking where a distress system needs to survive a crash in order to function. I hope this is of some help. Regards - Dave Blackwell, CEO Spidertracks.

[Old Akro]

Depending on the GPS engine and how much the unit was moved since it was last turned on, it can take several minutes to get a GPS lock. If it has not been turned on long enough to get satellite lock, it may not send its message.

[Dick Smith]

The GPS was locked as the green led was on.

Buzz. I don't think you understand. I am not concerned with a delay in sending the message. I am concerned with it not being received in the first place .

I simulated a typical emergency situation where power could be lost to the unit 2 minutes after the distress button was pushed. In this case no message was sent. My question is why?

Was it because iridium can have a queuing system when lots of messages are being sent and this means there can be a delay of 2 minutes or more before the message is received by the satellite in the first place.? This time delay, if it exists should be known.

[Dick Smith]

If a pilot wishes to cancel the watch mode how long does he have to leave the battery switch on after the button is pressed to be assured the message is sent?

[AbsoluteFokker]

Even morse code had an acknowledgement of receipt message. This system is a joke if it doesn't have a receiver to ack responses and resend (ever wondered what QNH meant - it is related to the same family of messages!)

[MJA Chaser]

VK2DIK.
Send an emergency message out on APRS. Hundreds will get it. I think you can even ask for an ack.
VK2HRX

[spinex]

Thanks STL, good to get an understanding of the system, its limitations and indeed its strengths. Watch it is. I'm open to correction, but as I understand the system, even an ELT or EPIRB can fail to get a message out if it goes offline shortly after activation - eg airframe fire or the whole shebang slides beneath the waves and there is no feedback on reception either.

[Dick Smith]

I realise there is no 100% guarantee a spidertracks message gets through and that's a good reason for the flight following "fail safe "mode .

However there must be a worse case time delay in actually accepting a message by the satellite if it is loaded down with lots of traffic.

Surely iridium must know this figure.

[chopper99]

The problem with technology is that the better it gets the more we complain about its shortcomings. Who ever would have even thought about Spidertracks a decade ago? Now its not good enough? My thought is that if you need Spidertracks with perfect functionality to feel safe, you may be better off taking up golf.

Not sure that I agree with Aussie Bob's reply. The Aviation (and other) industry is driven by continuous improvement. That involves asking the right questions at the right time (and that is not whining). Questioning fuels innovation. I believe this is a very valid question, actually one (and a few others) I had asked myself when I was flying a Spider Track tracked Bell 206 in PNG and was watching over a few other pilots operating in very remote areas of PNG.

1.) How confident can I really feel that they will find me if things go quiet?
2.) How confident can I be that the Heli which shows on the map at the destination as "Landed" has not actually crashed unto the Helipad with the Pilot incapacitated and the battery still supplying power to ST, hence not triggering an alert.... (not every accident destroys the ST unit or its power supply and therefore triggering a post accident alert). I was also thinking of complex and extended Long Line Hovering work (if never going above threshold speed). Some of that exposed flying happens below the TH speed after you are reported landing).
3.) How much time do I have to send out an EMERG message when there is trouble with the Heli or the WX Options? (Yes we can try to maintain adequate height AGL but we have to land and take off (also think Long Line) and then time is short to initiate an EMERG message.
4.) Is there enough time to get a Pos Fix Message out in time to be meaningful for the search party looking for me in Broccoli country. Quick math, assuming a LongRanger traveling at 100 kts, at a reporting interval of 2 minutes it covers 3.33 NM, at a reporting interval of 0.30 sec. it cover 0.88 NM of distance. Combine that with inevitable GPS inaccuracy, a Helicopter Pilot working weather........ If you have ever searched for a downed aircraft in the Jungle of PNG, Broccoli country, 2-3 Tree canopies (think small 206 fuselage) you know what I mean.
5.) What if I have a Fire ans just shut down my tracker as I am rapidly descending...... that does not make sense....
6.) There were more more....

Anyhow I said to myself, with today's technology and with the monthly subscription I am paying, as an Ops Manager, I ought to get a whole lot more information back from the fleet than what I am getting. I came across the NZ tracking Company V2Track.com that was offering a Hybrid SAT/Cell tracking solution and asked them about some of the additional features I was looking for. They were super helpful and listened to all my questions and added features. I liked the Cell Tracking option not only for the cost savings but also for the more responsive Cell technology, the reduced time it takes for a signal to go out and be received but also for the much higher reporting rate (adjustable).

Some of the other features which the V2-Tracker offers are the capability to receive and appropriately interpret 3 +2 additional digital inputs:
1.) Collective Switch
2.) Engine OUT
3.) M/R RPM LOW
4.)Battery Voltage
5.) Rate of Turn Sensor
Between the above digital inputs and the built in "Rate of Turn Sensor" the compact SAT/Cell Tracker has become "semi smart". Meaning it can and will automatically trigger an EMERG message with intelligent notes always including Coordinates and geographic reference to a know waypoint, (P2-XYC has experienced an Engine failure at 6SW of LWKY), so even a lay person can make sense of it. The automated triggers can be:

1.) Engine Failure
2.) T/R Failure
3.) M/R Over torque
4.) Generator Failure
5.) Emergency Descent (faster than a preset threshold (2000fpm)

All of that without the Pilot ever lifting a finger (try pressing an EMERG button when loosing a T/R in a 100 ft Long Line Hover over a confined area or on the side of a cliff).

Besides all of that a Garmin GPS can be interfaced and now home base always knows the Track, ETA Next WPT, and so on in real time.

Besides that the system always indicates the status of the Helicopter (Battery On, Engine On, Hovering, Cruise...) based on real parameters and not just a threshold speed.

Not only is this info very helpful when everything is going well but think about when there is an accident and people are trying to piece together the puzzle of what happened.

There is also a very sophisticated Messaging, Electronic Flight Bag Messaging App, (always with Transmission completed confirmation) and a bunch of sophisticated Tracker and Monitoring and tracking web site feature.

Yes if there is no Cell coverage (and PNG has a rather impressive coverage by now, and is still increasing) worst case is, it will automatically switch to SAT (Iridium) mode and now you have similar issues and challenges to ST (as already discussed on this forum).

On the subject of when and if at all turning the power off to the tracker. We installed V2 with the option (3 position switch, Buss, Off, Battery direct) this way the pilot can switch (SOP's) to Battery direct mode and turn the A/C buss off and continue to get tracked all the way down and beyond if desired.

In my book ST is the easy and quick (up front) solution for getting an A/C going operationally but it seems more suitable for recreational, flat and developed country F/W flying where proximity to terrain as well as complexity of operation is not as much of an issue and there is ample time to get the message out or make an emergency landing.

Needless to say we have switched our whole fleet over and I have a new degree of confidence and sense of satisfaction in the quality and quantity information which I am getting sent back from the Helicopter . The Price point and weight are slightly more but very comparable and usually you only find these sophisticated features in much heavier and more expensive units. So this makes this system also an ideal fit for installation in a lighter Heli such as a Robby and even quicker in it's response time when used in a fairly developed country such as Australia. Of course the installation requires an EO but it does not have to be installed, it can be Velcro mounted and plugged in to move between A/C (now without the digital inputs). Of course the more you operate in Cell covered areas the bigger the savings as you pay per Sat report.

If we stop asking questions we stop learning and stop improving.

Regards,
Chopper99

[Derfred]

Dick, I think the problem is you are asking for a "worst case" for a statistical parameter. There is no such answer.

It's like asking, if I toss a coin multiple times, what's the maximum number of tosses before I toss a "head". I could give you a 95 percentile answer, or a 99 percentile answer, but the 100 percentile answer is "approaching infinity".

You don't know what sort of network congestion could be occurring at the moment you press that button, and neither do Iridium. All they can give you is statistics.

You are asking for a guarantee from a one-way comms solution that only a two-way comms solution can provide.

It's a bit like asking what's the worst case delay for submitting my census form? :}

[AbsoluteFokker]

Ahh - these are one-way communication systems so no ACK capability. I note that Spider6 and Spider7 units can receive texts - surely an ACK of the SOS button would be a useful capability.

These are certainly questions best aimed at Spidertracks rather than a forum though... please report back with their responses.

[Dick Smith]

STL from Spidertracks has explained it clearly. Delays up to 5 minutes.

What this means is that you can't rely on the emergency function to get a message through in an emergency if the power supply is likely to be turned off in that 5 minute time.

So if you need to guarantee SAR the sensible and only reliable way is to use the "watch" function . I will do that when I need a fail safe service.

I think Spidertracks is a great system - but it's important everyone understands the best " fail safe " way to operate it.

Derfred. The one way coms will most likely provide a fail safe SAR service if the watch function is utilised.

[BuzzBox]

The one way coms will most likely provide a fail safe SAR service if the watch function is utilised.

Well there you go. Isn't that what I suggested to you in the first place??