High speed ILS approach


My strategy for doing a high speed approach is as follows:

1. Figure out the altitude at which you'll be cleared for the approach: in a big city airport, its usually the farthest out waypoint and the highest spot on the profile view: e.g., at Boston Logan its 3,000 feet and at Chicago Midway its 4,000 feet. Listen to the instructions being given to the other traffic for a good clue.

2. Set power at that altitude at 2,600 rpm and fuel flow at 15.5 gph. This will yield 160-163 KIAS at 4,000 feet or below.

3. By the time ATC starts issuing vectors to intercept the final approach course and you're within 120 degrees of that course, hit VLOC on the Garmin, confirm that the proper course heading is set for the HSI, and then hit HDG and NAV on the autopilot. The APR annunciator should go on automatically.

4. If there are multiple waypoints left before reaching the outer marker, don't hit "Activate Vectors to Final" on the Garmin: it will wipe out those extra waypoints from the flight plan and you won't have a distance readout, which may be necessary if ATC asks you to contact tower at a point prior to the outer marker (this happens all the time at Chicago Midway). Instead, just hit "Activate the Approach" on the Garmin to preserve the waypoints; be careful not to do this if the NAV GPSS is still engaged, because then it will fly you straight to the first waypoint in the approach, which will make ATC very upset. Also beware that you'll probably have to manually set the approach course heading for the HSI, since the Garmin only sets this automatically if you hit "Activate Vectors to Final".

5. Maintain the power setting noted above until the glideslope is actually intercepted, e.g., the white arrow is in the center of the vertical readout. Then (and only then), as the autopilot pitches down the nose, pull the power lever back. If you want to descend at 140-150 KIAS, then go to 17 inches MP. If you wan to descend at 120-135 KIAS, then go to 13.5 to 14 inches MP. Once that power change is made, I turn on the landing lights, turn on boost pump and push the mixture to full rich (unless its a high altitude airport, in which case I move mixture up by maybe an inch).

6. Now, to slow down to flap speed, use the autopilot (which is determined to hold the glideslope) and the power lever to do the heavy lifting. No matter what speed you've chosen for the descent, once you pull the power to idle the speed will drop within one nautical mile to 120 KIAS; at that point I quickly drop in one notch of flaps and put power back in to 13.5 inches MP. The speed will soon stabilize at 105-110 KIAS, so I'm now in a position to drop in the second notch of flaps, or simply pull the power again once past the decision height and slow down further to landing speed. I don't disconnect the autopilot until the DH, or below the clouds; and remember that full flaps are not permitted if the autopilot is engaged. If its a long runway, I sometimes come over the numbers at 90-100 KIAS and spend the first 3,000-4,000 feet slowing down before landing. But if they ask for an intersection turnoff, then I use the last half mile after the DH to get the speed down to 75-80 KIAS over the numbers and make believe its a short field landing.

7. Depending on how low the ceiling is, how busy the traffic is, and how comfortable I feel with the situation, I'll do the big power pull described in paragraph 6 typically at 2.5 to 3.5 miles from runway (using the Garmin for this distance information). You've got to practice this in VFR conditions several times to get comfortable with the sight picture and the power/flap settings, and eventually you'll trust the fact that the plane can actually slow down that rapidly in only one nautical mile.

I recommend doing this kind of high speed approach only with the autopilot on; and only with an ILS. Word of caution to everyone (but especially low time pilots): before trying this get a few dozen approaches under your belt, and be really dextrous with the Garmin, PFD and autopilot.