IFs ands or buts...

Notice the dual capital in IF in the title? I'm talking about Intermediate Fixes, or IFs, established on final approach courses, 'round about the 10NM mark on instrument approaches. They were established a few years back on many approaches across Canada in a bid to aid aircraft equipped with RNAV (including INS, GPS, and so forth) to allow them to make their own way to the final approach course without having to fly over traditional NAVAIDs or use things like those ugly DME arcs. The arcs aren't so ugly as some transitions I've seen flown...

My point? There are a growing number of pilots taking liberties with these things. Some of the things I've seen include:
-Flying toward them from what would amount to a base leg heading, then turning to final as much as 4-5 miles back, thereby cutting down the time to fly on final, and possibly compromising the separation ATC is using to squeak a departure out in front of him.
-Coming at the IF from an angle sharper than base leg, making a turn difficult. The FMS solution is to project a fix out to generate a base leg fix. Problem is, they're not telling ATC about it, instead they just request "direct FIXXX" and do it without letting ATC know. If ATC had an aircraft on parallel radar vectors and expected them to fly direct FIXXX, as requested and cleared, it could get ugly.
-Heck, on several occasions I have even seen a pilot flying inbound to ADRET for R29 at CYQM from almost exaclty the opposite direction, meaning he's setting up for the ILS29 from right overhead the runway. One pilot told me about he planned a procedure turn at ADRET. The published PT is related to the QM NDB, which means his own PT was never assessed for obstacle clearance like the published one was.

It seems in the world of RNAV, some pilots just don't think about how they're actions relate to the airspace around them, or to their own goals, for that matter. From a pilot's point of view, it really is easy to tell a box to go directly to FIXXX and let her run. There are no rules published with respect to where and how to use IFs like there are for, say, circling procedures. Having said that, it would be nice to let ATC know what you're doing, if you aren't planning to do what you're cleared for. We do see many pilots requesting direct to fixes for approaches and then telling us they plan to do a visual when they get in closer, even using fixes associated with RNAV approaches they tell us they're not qualified to fly. That's just fine by me, since I know they're setting themselves up and keeping ATC informed. Just something to think about.

Odd Hold

Another thing that happened during the recent winter storm was an odd holding pattern. One airplane, inbound but not ready to land (who eventually chose to go elsewhere when the report he was waiting for turned out to be ugly) was issued a holding clearance. The hold went something like, "cleared to the Sumspot VOR via direct, hold west, inbound on the 270 raidal, expect further clearance at 1600". The idea was to get the airplane established for a race-track hold with the top of the oval heading inbond to the VOR on a 090 track (the 270 radial on the west side of the facility) and make a right turn of about 180° to go outbound. On the outbound leg, the aircraft adjusts his heading and outbound timing to provide an inbound leg, on the described radial, of approximately one minute.

The aircraft's solution was interesting. He flew inbound on the 270 radial, the appropriate track of 090. Over the VOR, he turned right. The right turn, which should have been 180°, was very wide and ended up being a turn of 225°. He flew this heading to intercept a track outbound from the VOR and parallel to the 270 radial on the south side, offset by about 4nm. Then, after approximately one minute, he made another wide right turn of about 225° which carried him through the 270 radial to the north side and the heading brought him back to reintercept the 270 radial for his inbound leg. This pattern was repeated with precision 4 times before he finally left. This implies that the FMS was driving the holding pattern, and that it was programmed inappropriately. Going so far through the 270 radial to the north side means that he was actually well outside the airspace that ATC would protect for his hold. In the radar environment, it is less critical, since we can see what he's up to, but it's still a surprise. In a non-radar environment, ATC could put someone nearby, provided the protected airspaces don't overlap. Given just how far this jet went from where he was supposed to be, it provided for a bad opportunity for a problem. Someone should be looking into why that hold went so far awry. Anyone know any more about why this sort of thing might happen? Please leave me a comment so we can learn.

Storm update, Gear problem

Last night's storm was largely uneventful. A Dash 8 departed CYSJ and told us on initial contact that they had "something they wanted to look at, but it wasn't an emergency yet". Interesting way to check in. Turned out the gear was stuck down (better than stuck "up") and they continued to destination at reduced true airspeed.

Aircraft with retractable gear have Vle, or maximum velocity with gear extended. This is not to be confused with Vlo, or maximum velocity for operating the landing gear, which means raising and lowering it. The difference is that when it's extended, it's down and locked, and many aircraft have small landing gear doors that are opened with the gear "in transit", and close again once the gear is down and locked. Exceeding Vlo might tear these doors off, perhaps damaging other aircraft components in the process, or overstress motors and hydraulic systems responsible for gear extension/retraction. Also, some aircraft have different maximum speeds for raising and lowering gear, depending on how the doors open, how the gear is extended, etc. For example, an aircraft with forward-retracting gear may have to be at a lower speed for raising the gear due to the extra drag encountered in pulling the struts forward, vs the push they get when dropping them with the wind. Some aircraft have little or no restrictions on this, such as the old, hardy Lear 25. Their gear was capable of being used at any speed as a dive break in an overspeed condition. There may be others, but that's the only one I'm aware of at the time of writing.Now if I can only get my car started after the storm...

Winter Storm, December 27, 2004

Well, here I sit at work. Storm stayed. Well, sort of. The snow storm raged throughout the Maritimes, where I work at Moncton ACC, and by the time the storm started to lift and the plows started to make their rounds, there would be little point to me trying to go home. We work a day shift and follow it up with a midnight shift, which is what I was scheduled for today. Let's see... Take 30-45 minutes to drive home, risking getting stuck in a snow bank in near zero visibility and all the compacted-snow-covered roads, take 1+30 or so to shovel my into the driveway, sleep for about an hour, then take another hour or so to shovel my way back out and risk the drive back to work for the night shift. I figure I might as well stay here for the time.

On the plus side, it should be an interesting night. Hardly any planes took off or landed in the Maritime provinces today, what with winds from the northeast at 40G50, visibility down around 1/4 +SN +BLSN, and the ceiling of VV003. Most runways were closed or covered with snow (to the point where works crews had their hands full) given the snowfall and the high winds. The midnight shift coming up should be interesting as they try to reposition aircraft once the airports open again -- especially since staffing on the midnight shift is low due to normal nighttime traffic patterns. If anything interesting happens, I'll be sure to mention it -- as long as it could be heard from a general public point of view. I'm technically not allowed to give out "secret" information. Anyway, time for some rest.

What is VatSim?

It's mentioned in the introduction header to my blog, but for those who find this blog without already knowing something about me and what this is all about, I thought I should introduce VatSim. Since I first started using Flight Simulator 20 years ago, I had heard of people wanting Air Traffic Control in the program. I never quite understood why. Several years ago, some software writers joined forces to create a method to get realistic ATC in Flight Simulator: Their idea was to write some programs to work together. With donated server bandwidth and space, the servers would run software that would host the network. Pilots flying Microsoft's Flight Simulator and some other programs would connect to these servers with a client program. Then, somewhere else in the world, people would connect to the same servers with a "radar client", allowing them to see a imulated radar picture of the aircraft connected with Flight Simulator. This way, folks could fly real time from Point A to Point B, while others flew from Point C to Point B, or Point D to E and so forth, and other people would provide ATC services for them. By using voice communication through the internet, another step to providing "as real as it gets" came to being. With over 40,000 members, VatSim remains free to the users on both sides, relying totally on volunteer efforts to keep the organization running in a trimmed down version of the real world offering the most realistic ATC possible. There are other networks that run similarly, but none has reached so many as VatSim. For more information, click on this link to get to VatSim's home page (http://www.vatsim.net).