Forums: Skydiving: Gear and Rigging:
Magnetic Riser Covers - interference with a/c compass calibration?

 


LavaLady  (F 387)

Jul 25, 2012, 9:17 PM
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Magnetic Riser Covers - interference with a/c compass calibration? Can't Post

One of our Aussie aircraft operators recently gave us notification of a perceived issue with magnetic riser covers (eg Sigma) interfering with compass calibration on jump planes.
He states that the problem goes away as soon as the jumpers leave the plane. They have found that they can minimise the problem by not putting anyone with that equipment near the front of the plane.
He feels that this is not a long term solution nor is it acceptable to continue operating with an unknown or variable quantity of magnetic interference in the aircraft.

Searching dz.com I have found a limited discussion on this subject - but from 5 years ago. http://www.dropzone.com/...371#2664371 Post #16.

So these covers have been in use for a few years now. Has anyone heard of any similar reports? (I have not) Specifically on whether there is any effect on aircraft compass calibration.
If yes, has there been any resolution?

Kim Hardwick
Technical Officer
Australian Parachute Federation

(PS. One manufacturer has also been emailed directly. Just making this post as well to broaden the research net.)


DBCOOPER  (D 24112)

Jul 26, 2012, 6:43 AM
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Re: [LavaLady] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Ever see what happens to the compass when you turn the landing light on?


milehigheric  (C License)

Jul 26, 2012, 7:47 AM
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Re: [DBCOOPER] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Whoa...Pilots still use compasses? Tongue


Premier Remster  (C License)

Jul 26, 2012, 8:23 AM
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Re: [LavaLady] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

In what kind of aircraft has this been observed? 182 type with some people sitting right up to the front?


Premier billvon  (D 16479)
Moderator
Jul 26, 2012, 10:55 AM
Post #5 of 19 (1886 views)
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Re: [LavaLady] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

In reply to:
One of our Aussie aircraft operators recently gave us notification of a perceived issue with magnetic riser covers (eg Sigma) interfering with compass calibration on jump planes.

Just a quick note - while magnetic riser covers (or any magnets, or any metal) can affect an aircraft's magnetic compass, none will affect an aircraft's directional gyro, which is what most pilots use as a compass. Traditionally the DG is aligned to runway heading before takeoff, and the magnetic compass is used only when the DG fails or precesses a bit during a long flight.


wayneflorida  (D 30566)

Jul 26, 2012, 11:11 AM
Post #6 of 19 (1875 views)
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Re: [billvon] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

In reply to:
In reply to:
One of our Aussie aircraft operators recently gave us notification of a perceived issue with magnetic riser covers (eg Sigma) interfering with compass calibration on jump planes.

Just a quick note - while magnetic riser covers (or any magnets, or any metal) can affect an aircraft's magnetic compass, none will affect an aircraft's directional gyro, which is what most pilots use as a compass. Traditionally the DG is aligned to runway heading before takeoff, and the magnetic compass is used only when the DG fails or precesses a bit during a long flight.

Personally I set DG by compass and confirm runway heading before takeoff.


RiggerLee

Jul 26, 2012, 12:14 PM
Post #7 of 19 (1849 views)
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Re: [wayneflorida] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

I'm not sure I see this as an issue. Magnetic deveation can come from a lot of sorces. It's also very dependent on the mounting and location of the compass. When we replaced the compass in my airplane we looked at changing it's mounting location. There wasn't enough athority in the adjustments to allow it. Every system on the aircraft affects it in one manner or another. Generally speeking it's set and calibrated in one perticular configuration ie. with the systems turned on in the configuration you would expect for IFR flight. Any change from that for example not haveing your nav lights on or not haveing all of your radios powerd up or turning the landing lights on will create an error. Even then in the best case there is ussally a writen table of corections in the plane, generally on a sticker under the compass.

Basically I don't see where this is such a big deal. Skydiving is generally a VFR activity conducted in a famillior local enviroment. Just deal with it. In the rare event that you are traveling cross country with jumpers on an extended flight, ferrying an air craft in IFR conditions just ask them to stow the rigs in the back.

Lee


riggerrob  (D 14840)

Jul 30, 2012, 7:34 AM
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Re: [RiggerLee] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Agreed!
All skydiving flights should be VFR and close to home base, so directional instruments are not THAT important.
Magnetic compasses are the third or fourth most important directional instrument, after: directional gyro, GPS, VOR and eyeball.


Skybear

Jul 30, 2012, 8:19 AM
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Re: [riggerrob] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

I suggest to leave this decision to the pilots. They are flying the aircraft so they have the authority about how to operate it safely.


Beatnik  (D 1051)

Jul 30, 2012, 5:15 PM
Post #10 of 19 (1601 views)
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Re: [riggerrob] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

In reply to:
All skydiving flights should be VFR and close to home base, so directional instruments are not THAT important.

I just want to throw in that not all flights are VFR and some can't. For instance, high altitude jumps when you get into Class A airspace. No VFR there just IFR. Now for the most part that is not that common and most flights are VFR but that shouldn't rule out the importance of instruments.


riggerrob  (D 14840)

Jul 31, 2012, 7:16 AM
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Re: [Skybear] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

In reply to:
I suggest to leave this decision to the pilots. They are flying the aircraft so they have the authority about how to operate it safely.

.......................................................................

Call me a retired jump-pilot.


DBCOOPER  (D 24112)

Jul 31, 2012, 6:07 PM
Post #12 of 19 (1451 views)
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Re: [Beatnik] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

There is a big difference between IFR and IMC. And I don't know very many pilots flying IFR by compass these days...


LavaLady  (F 387)

Aug 1, 2012, 9:33 PM
Post #13 of 19 (1364 views)
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Re: [LavaLady] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Quote from the CI of the operation at which this issue was first observed/reported:

"This issue has emanated from my own DZ where we utilise a C-206. Up until 3 weeks ago we were jumping the original Sigmas with the Tuck Tab design Riser Covers, however we have slowly been upgrading with a retro-fit kit from UPT. So far we have only 3 out of 8 Sigmas with the modifications.

The original interference was noted by our pilot and was quickly diagnosed by the staff. There has been testing done by the staff and pilot in the meantime to find a workable solution to ensure the matter does not become a danger or inconvenience to anyone involve.

At this stage we are operating with a skeleton staff of 2 TMs which makes the issue a moot point as the seating arrangement with 2 Tms does not require the use of the seating bench that we have been using. The bench in question sits beside the pilot and is approximately 380mm tall and runs lengthwise from 300mm behind the leading edge of the rear door and forward to the dash. The problem only becomes clearly evident when the tallest TM (6'4") sits on the bench which bring the magnets in close proximity to the compass.

I have spoken to our pilot, who is monitoring the situation and will ensure that the situation does not cause any adverse effects to the operation of the compass.

A changing in the height of the bench is being investigated, so when we have 3 TMs in the aircraft, all will be able to remain out of the immediate proximity of the compass and prevent interference."



Yorick  (D 108976)

Aug 2, 2012, 4:01 AM
Post #14 of 19 (1339 views)
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Re: [LavaLady] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

In reply to:
Quote from the CI of the operation at which this issue was first observed/reported:

"This issue has emanated from my own DZ where we utilise a C-206.

The original interference was noted by our pilot and was quickly diagnosed by the staff.

The problem only becomes clearly evident when the tallest TM (6'4") sits on the bench which bring the magnets in close proximity to the compass.

Can you give more detail about the behavior of the compass?
Does it turn 180 degrees or just a few?


erdnarob  (D 364)

Aug 5, 2012, 2:53 PM
Post #15 of 19 (1248 views)
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Re: [billvon] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Like all gyroscopes, the directional gyro or heading indicator will have a drift after a certain time, therefore the directional gyro or heading indicator has to be reset manually every 15-20 minutes to match the compass when flying. Provided being in a straight level flight, the compass is a reliable device and has to be calibrated every 12 months by an aviation mechanics. The mechanics establishes a compass correction card as well mentionning if the correction was been done with radio on or off. The airplane compass has also a logbook to record each calibration. I am surprised to read that the use of compass in aviation seems to be old fashion for some readers. When you lose electrical power on an airplane (that happened to me), you lose the vaccum pump which drives all gyroscopic devices including the DG but your compass is still working. I am speaking about Cessna airplanes but basically, other airplanes have similar systems.


DBCOOPER  (D 24112)

Aug 5, 2012, 3:52 PM
Post #16 of 19 (1230 views)
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Re: [erdnarob] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Yea, I remember doing compass turns during instrument training and yes it's a tool in the tool box but in this day and age if your relying on a compass as your only backup you shouldn't be in the clouds, and you sure don't need one to fly jumpers.

Set the DG to runway heading and climb for 20 minutes and your problem jumps out.Angelic


theplummeter  (C License)

Aug 5, 2012, 10:27 PM
Post #17 of 19 (1187 views)
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Re: [DBCOOPER] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

Compasses stopped being relevant when they stopped filling them with whiskey Wink


erdnarob  (D 364)

Aug 7, 2012, 9:21 AM
Post #18 of 19 (1097 views)
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Re: [theplummeter] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

And flying over the North pole !!CoolCool


erdnarob  (D 364)

Aug 7, 2012, 9:25 AM
Post #19 of 19 (1095 views)
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Re: [DBCOOPER] Magnetic Riser Covers - interference with a/c compass calibration? [In reply to] Can't Post

BTW I have the DB COOPER #290 certificate from jumping out of the Boeing 727 in 1992 at Quincy Ill. We were 180 people in the airplane. I jumped it again in 1998. Later on I added the DC9 by doing two jumps out of it in 2006 at Rantoul Ill.



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