Originally Posted by
Ajax
ok..let me see if I can explain this without scaring the crap out of you.
Haha, come on now! We can take it!
Originally Posted by
Ajax
I'm going to throw a question out to you pilots...are you able to safely fly on final and land behind a heavy/B757 with less than 5 miles by staying "above" the descent profile of that heavy? I may be wrong, but I was under the impression that if you stayed at a higher profile/angle, and touched down at a point further down the runway than the heavy, that you would stay above such wake. Again, I'll confess I'm not a pilot, so I may be misinformed on this.
Yup, completely true. Generally speaking, the wake turbulence of any aircraft starts to sink not long after it's generated. When following a heavy (or hell, even a super), staying above the preceding aircraft's flight path will ensure that you avoid its wake. The practice in this scenario would be to fly a dot above the glideslope and aim to touchdown towards the end of the touchdown zone. However, this practice of flying a dot high is something we can only really do in good VFR weather, as in IFR weather we are required to stay on the IFR approach profile/glideslope until visual with the landing runway.
Again whether or not a flight can accept this practice of staying visually behind/above a heavy -- depends on the pilot! Flying above the glideslope is something that has to be handflown, as the autopilot has no practical way of maintaining vertical control at lower altitudes (below, say, 2000ft) if it's not following the ILS LOC/GS, and it can't be set to fly an offest from the ILS center beam (at least no aircraft that I've seen). Every airline has it's small share of "lazy" types that cannot be bothered to hanfly the aircraft, and will not turn off the autopilot until they absolutely have to. Flying an RJ in and out of JFK for the last several years, I'm very well versed in this practice, as are most of my colleagues. However there are some that won't do it, mostly out of laziness, and will not take a visual behind a heavy (at least without some serious spacing).
I've heard of instances where an aircraft's wake has hit the runway surface and then bounced back up into the air, above the generating aircraft's flight path as it enters the flare. However, this is only likely to be an issue for a light piston driver following a little too closely behind a large jet.
Originally Posted by
Ajax
In the past we did on ocasion, but after CRDA rwy 11 final was created RWY 11 arrivals are only ILS11.
CRDA RWY 11 -- what is that like a position or something? Does CRDA stand for anything?
Hey speaking of lousy JFK ILS13L, LGA ILS13, TEB no-go type days, today looks like one of them. Have wx/winds like this ever gotten so bad that EWR would be up and down RWY 11 only? I understand some jets (typically heavy) can work with 35ish kt crosswinds, however for most transport category aircraft, the max demo crosswind is around 30kts. I know BTA, one of your most frequent customers, can only work with 30ish as that's the max-demo xwind component on a E145. CAL's mainline jets can probably do 30-35, but I can't speak for Boeings.
Originally Posted by
Ajax
Which brings me to another observation. Watching the Singapore heavy coming from Kuala Lumpur go around because of a conflict with a Rwy 11 Colgan arrival that took off 35 minutes ago makes me cringe my teeth every time it happens. Not fair but its just easier for the tower to have a 22L go around than the 11.
I'd be ****ed too if I just flew 18 hours and had to go around because of Colgan, lol! BTW, that flight comes in non-stop from Singapore, but I know what you're getting at.
Regarding 500' separation with a VFR target and TCAS RA, here's what I can tell you (and btw, this is pretty much standard amongst all FAR121 airlines. I'd imagine foreign carriers abide by the same):
1. If given a TCAS corrective RA (i.e. CLIMB, CLIMB/DESCEND, DESCEND), we MUST comply with the command unless it would be considered UNSAFE to do so. Our manual warns us not to ignore a corrective RA when having an aircraft visually in sight, as the aircraft we're seeing may not be the aircraft generating the RA. Also, TCAS commanded climbs/descents MUST be handflown (autopilot reaction time too slow, as George is programmed to fly smoothly).
2. Generally speaking, a corrective RA will only be issued when the TCAS detects any sort of vertical converging (i.e. loss of vertical distance between a target) -- i.e one of the aircraft involved is climbing or descending at a rate which causes the TCAS to compute that a conflict is probable in under 30 seconds.
Simply passing a steady 400-500ft above/below a target will usually not trigger a corrective RA if both aircraft are steadily maintaining altitude. This may, however generate a preventive RA (ADJUST VERTICAL SPEED/MONITOR VERTICAL SPEED), in which our TCAS/vertical speed indicator will will light up red in the direction of the target (upwards if the target is above, downwards if below), telling us, hey, you've got someone minimally separated above/below you -- do NOT climb/descend (again, depending on whether the target is above or below). In this case, we're not likely to vacate our assigned altitude.