I have heard several times about people DFing in IFR conditions. There have even been a couple of posts here about it. How exactly does one DF on an IFR Flight Plan in IFR conditions? Or did I misnderstand?
You don't, at least not in these parts.
We've got pilots that could probably handle it, but the ORM numbers are so high as to generally preclude flying, especially at normal search altitudes - in most cases we roll more ground assets and the flight crews stay home until the weather breaks.
Theoretically, though, it wouldn't be much different - the Becker's and L-Pers would work just as well, and a heading is a heading.
Have been part of a crew that DF'ed in IFR. The difference is that you are not trying to spot it on the ground, rather you are trying to isolate it to a lat and long that a ground team can respond to.
I've been on a couple of ELT missions in IFR conditions. It was strictly electronic search, didn't even try to get a visual.
We usually operated at the IFR minimum vectoring altitude and always under radar surveillance.
The FAA usually had no problem working with us, they felt that they were participating in the mission with us and made sure we were safe.
Usually we filed to a point in the search area and then went to flight following while we were acquiring and tracking the signal.
There's a few different tactics. Like above, you can do a fairly standard electronic search from a safe altitude with solid ATC oversight in relatively clear airspace.
If you can't maneuver so much, you can still cone down... that is find the acquire & loss points, go a little lower & repeat, alternate N/S & E/W... and you can narrow it down.
If you can't fly at all, I've had ATC get info from in/out bound airlines about altitude at signal loss. With enough data points, you can narrow it down a bit.
Quote from: DNall on November 02, 2008, 06:48:01 AM
There's a few different tactics. Like above, you can do a fairly standard electronic search from a safe altitude with solid ATC oversight in relatively clear airspace.
If you can't maneuver so much, you can still cone down... that is find the acquire & loss points, go a little lower & repeat, alternate N/S & E/W... and you can narrow it down.
If you can't fly at all, I've had ATC get info from in/out bound airlines about altitude at signal loss. With enough data points, you can narrow it down a bit.
We were doing it in California in mountainous territory. Hence staying at or above the min vectoring altitude.
Flying into a mountain while chasing that little needle does nothing for the victims.
Granite clouds can really mess up an airplane's paint job! :D
Quote from: PHall on November 02, 2008, 05:03:49 PM
Quote from: DNall on November 02, 2008, 06:48:01 AM
There's a few different tactics. Like above, you can do a fairly standard electronic search from a safe altitude with solid ATC oversight in relatively clear airspace.
If you can't maneuver so much, you can still cone down... that is find the acquire & loss points, go a little lower & repeat, alternate N/S & E/W... and you can narrow it down.
If you can't fly at all, I've had ATC get info from in/out bound airlines about altitude at signal loss. With enough data points, you can narrow it down a bit.
We were doing it in California in mountainous territory. Hence staying at or above the min vectoring altitude.
Flying into a mountain while chasing that little needle does nothing for the victims.
Roger. There still a little bit you can do to narrow the search area that doesn't involve you turning circles anywhere near mountains. You can do a whole lot to make life easier on a GT w/o any directional & from altitude. It's just harder & more time consuming.
Here in the flat land we don't have granite problems but do have very tall antennas. In any case, a safe IFR altitude and cooperate ATC is all that's needed for an electronic search. I have done them with experienced crewmen even at night. Yes the ORM numbers jump but it is no different than any other night IFR flight. Everyone must do their respective job for the mission to be successful and safe. The pilot flies, Observer manages the mission (Becker & CAP radio) and scanned keeps the paper work.
The CAP radio must work in this scenario since visual direction methods aren't an option for ground team communication.
This time of year IFR at night is a real possibility since daylight time just switched off and our sunset is around 1730. With colder temperatures the potential for ice goes up too which is a big no go.
One more note, the ground team needs a GPS and someone who knows how to use it. That's the only guidance the aircrew will be able to give then. Telling them you're 22.5 miles from a VOR on the 230 degree radial wouldn't help but the Lat and Long from the aircraft GPS and general location but dialing down the map scale would help. Most GPS's identify some roads which could help narrow down a location.
Actually, 22.5miles at 230 from a VOR would be fine. They're going to plot your GPS coordinates on an expired sectional anyway, and then try to figure out what roads run near there, and what airports fall into that possible area.
Quote from: sparks on November 03, 2008, 02:04:07 PM
One more note, the ground team needs a GPS and someone who knows how to use it. That's the only guidance the aircrew will be able to give then. Telling them you're 22.5 miles from a VOR on the 230 degree radial wouldn't help but the Lat and Long from the aircraft GPS and general location but dialing down the map scale would help. Most GPS's identify some roads which could help narrow down a location.
Why the need for a GPS? Shouldn't the ground team be able to plot lat and long on their maps?
About 20 years ago I was on a ground team when this exact thing happened. The search area was fogged in, but our aircraft was able to get on top where it was clear. They weren't in the soup themselves, but had no visual with the ground.
They gave us radials off of two VORs. Where they crossed was where we started our search. We had to do some old-fashioned map work (GPS didn't exist then) to translate it from our sectional to our other maps, but it was easy enough to do and got us close enough to acquire the signal. We had a couple of things going for us, it was daylight and it was clear on top. The trick was translating what the aircrew was able to give us into something useful on the ground.
Quote from: Flying Pig on November 01, 2008, 09:10:28 PM
I have heard several times about people DFing in IFR conditions. There have even been a couple of posts here about it. How exactly does one DF on an IFR Flight Plan in IFR conditions? Or did I misnderstand?
Do you mean IMC? IFR = not likely, unless you have a very unique situation like being the active aircraft in a positively controlled SUAS (i.e. the area is "hot" because of you). Flight test aircraft above FL180 in restricted airspace is an example. But I would not expect such a condition for us.
Procedurally, DFing in IMC would be essentially the same, only your position fix would be harder to get. (GPS or radial/DME) You still center the needle - but I think it's absolutely dumb to do in IMC.
Relative bearing using the needle deflection on an established track is not accurate. The deflection magnitude is proportional to the raw receiver signal, antenna patterns, RX dynamic range, ect, and is therefore highly non-linear with respect to bearing. You will not get an accurate radial while on a waypoint-waypoint ground track. One divsion might = 1 degree, two = 3 degrees, three = 8 degrees, and the like. Stronger signal will further delineate it.