Helicopter geophysical survey pilots?

[Steekvlieg]

Are there any helicopter pilots that can share "a day in the life of a low level geophysical survey pilot"?
Information from a pilot's point of view including tips and personal experiences during the operation.
What kind of flying is expected and how does the GPS system work to follow flight lines?
Any information that can help aspirant survey pilots understand what is expected from them.

[Bladestrike]

Some of thee funnest flying I have ever done! Spent one summer towing a bird in Northern Quebec in the late eighties, Longranger L1. Longlining skills don't come into play much, generally you are setting it down in a farely large area and I never bothered hanging my head out the door much for the pick-up/set-down, just used the rad alt, as long as it's not swinging (you should know how to stop/control swing prior).

We flew lines navigating from portable VOR stations we set up, keeping the rad alt at 200 feet to keep the bird (on a hundred foot line) out of the trees (not many trees over a hundred feet in Northern Quebec). It could be tricky in the hills, but we flew some 8 hours a day or more, so you get the hang of it quick. It was a fun summer!

[fijdor]

Some flying skills are required, you will have to fly straight precise lines at a certain height and speed as well, following your GPS display with limits on each side of that line. Your operator/customer will let you know what the parameters will be. Like bladestrike said you will probably be flying at 200 feet AGL putting the bird/mag or whatever system you will be using at 100 feet AGL so make sure you look outside for obstacles like power lines, towers etc.

In the mountains you'll have no choice on how you are going to cross that ridge, the orientation of the lines dictate the route you will follow, crosswind/upwind/downwind doesn't matter, you have to follow that display.

Some days you will get some good hours, some nothing at all because of the real weather but also from the "virtual weather" meaning there are magnetic storms out there that will affect the system (if that is still a problem today).

the idea is to fly an exact straight line at 200 feet AGL ( 50 meters max on each side for limits)and 70 kts while the system shoot a signal down toward the ground and picks it up again every let say 1 second, if you exceed the 70 kts then there will be too much spacing in between the readings, if you go too high the signal will not be strong enough or won't go deep enough to get a reading and of course if you get too low well there goes $75,000, spread all over the country side.

That's roughly what it is

Some guys get in there and do it, some just can't get the hang of it.

have fun, just curious what type of aircraft and the type of system?

JD

[RVDT]

Aero radio mag................

Rule 1/ Don't trash the bird.

Rule2/ Repeat rule 1..............

Like fijdor sez, some get it, some don't.

The issue is you are only allowed a certain amount of error in the flight lines. As the equipment gets better, differential GPS etc and better resolution in the survey equipment, the flight lines can get closer together and the allowable errors get very small. 40 meter line spacing was the most detailed when I was doing it many moons ago. You are working with sub 1 meter accuracy with the GPS in some cases. If the errors are too big the customer has the option to ask you to re-fly the job. Hardly profitable. If the pilot is not up to speed he will be replaced.

You are normally working with 12 channel GPS with differential correction either ground based or these days satellite based. Fugro seem to have the satellite correction tied up as they provide the service to themselves and sell it on to others.

It helps if you are happy/competent flying low level (wires) and heavy. The helicopter component of the job might only be a small part of the logistics required. The survey equipment probably costs a lot more than the helicopter. You are normally looking for magnetic anomalies and recording gamma ray spectrometry.

Sometimes you may end up, due to performance limitations of the aircraft, with 90 degrees of drift. Left/right becomes fore and aft and pitch becomes left/right. Of course as you speed increases this has to slowly return to normal or a lot less drift. (All the while maintaining your flight line and height.)

In the old days with the equipment we had the Rad Alt was in one display and the flight line was in another with a cross track error needle like a VOR which was a command bar. Above that was another needle in the opposite sense, it was a trend needle. If you joined or kept the needles joined everything was cool. The sensitivity could be shown by just yawing the aircraft with the pedals you could see a needle movement as the GPS antenna was on top of the tail fin.

Due to the fact that there is only so much equipment available to do this type of work you may find that you are constantly working with a prototype or one-off device. You need to understand the foibles in each piece of gear which can be vastly different.

You will be working with geeky types who speak another language. In their time off they probably read electronic component catalogues or "GPS World magazine".

It can be extremely challenging/boring flying. Imagine doing a survey at 40 meter line spacing in the flat desert for about a week. There is nothing to see and the only reference you have is the survey positioning equipment!

Alternatively check out fijdor's work on You Tube at up to 20K'. Wild, yet personally knowing fijdor he has the right temperament and experience to get it done in my opinion.

Go into it with your eyes open and if you can second guess the customer and get it right 95% of the time you should be OK. Just keep in mind that you might not! It is like flying the bottom of an ILS at decision point all the time only about twice as difficult.

There is a trend to fixed wing these days in the flatter country. Also there is a trend to smaller (cheaper) composite (low electronic/magnetic noise) aircraft as well. The survey companies will look at anything to get better data.

You will probably never see the final results of your work which can be frustrating for some. It is obviously expensive and very proprietary info!

[Steekvlieg]

Thanks for all the info.
The system will be a composite boom mounted laterally on the belly of a AS350.

[fijdor]

Ok you mean that kind of system, this the last survey job I did, 30 meters left/right 60 kts and 3 meters AGL, be careful in the turn at the end you don't want hit the system while turning trying to catch the next line.

JD




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