Control of Aircraft — Page 333, Lesson 439

I want to walk you through the Surveillance Radar Approach, or SRA — a non-precision approach procedure that uses Terminal Approach Radar, which we call TAR. Let me start with the key definition. An SRA approach is a non-precision procedure using TAR, and because it's non-precision, it will have a determined MDA/H — that's Minimum Descent Altitude or Minimum Descent Height. That's the lowest altitude you're allowed to descend to on the approach without having the runway environment in sight. Now, the procedure itself. The SRA is similar to PAR — that's Precision Approach Radar — but there's one critical difference. In an SRA, advisory height information is passed to you along with the range information. So the controller will say something like, "5 miles from touchdown, you should be passing one thousand five hundred and fifty feet." That's the advisory height — it's telling you what you should be at, not commanding you to be there. It's guidance, not a hard instruction. And here's an important operational point: SRA approaches always have an RTR — that's Radar Termination Range. The RTR is the point at which the radar service terminates, and you must have the runway in sight by then or you execute the missed approach. Let me show you what this looks like on a real chart — this is the SRA approach for London Gatwick, Runway 08L. Look at the chart details. The RTR here is 2 nautical miles — that's the radar termination range. The approach is flown on a heading of 080 degrees. The SDF, which is the Step Down Fix, is at 4 nautical miles. The MAPt — that's the Missed Approach Point — is at the RTR, 2 nautical miles. Now, the radar advisory heights table. This is the heart of the SRA. It gives you, for each distance from touchdown, three things: the altitude or height you should be at, the groundspeed in knots, and the rate of descent in feet per minute. At 5.0 nautical miles from touchdown, you should be at 1745 feet altitude, which is 1550 feet above the airfield — that's the HGT, height. Your groundspeed should be 160 knots, and your rate of descent 800 feet per minute. At 4.0 nautical miles: 1445 feet altitude, 1250 feet height, 140 knots groundspeed, 700 feet per minute descent. At 3.0 nautical miles: 1145 feet altitude, 950 feet height, 120 knots, 600 feet per minute. At 2.0 nautical miles: 845 feet altitude, 650 feet height, 100 knots, 500 feet per minute. And at 1.0 nautical mile: 80 feet per minute descent — wait, let me re-read that. At 1.0 nautical mile, the rate of descent is 400 feet per minute. The table shows the descent rate tapering as you get closer. Now, the OCA — that's Obstacle Clearance Altitude — and OCH, Obstacle Clearance Height. For the total area, you have two values. For aircraft categories A and B, the OCA is 845 feet, which is 650 feet above airfield level, and the OCH is 802 feet, 600 feet above. For categories C and D, the OCA is still 845 feet, 650 feet, but the OCH is higher — 1102 feet, 900 feet above. So the heavier, faster categories get a higher obstacle clearance height. The gradient is 4.9 percent, which is 300 feet per nautical mile. And there's a critical limitation: the maximum IAS — Indicated Air Speed — for the Missed Approach Procedure is 250 knots. Now the missed approach itself. At the MAPt, which is the RTR at 2 nautical miles, you climb straight ahead to 3000 feet, then as directed by radar. And there's a radio failure procedure — RCF, Radio Communication Failure. In the event of RCF, you climb straight ahead to I-GG DME 10 — that's a DME distance of 10 nautical miles from the I-GG beacon. For aircraft unable to receive DME I-GG, you use VOR DME MAY on radial R356. Then you proceed to VOR DME MAY, not above 3000 feet. The initial and intermediate approach are flown as directed by radar — that's the whole point of a radar approach, the controller is vectoring you. Let me also note the chart's other data. The transition altitude is 6000 feet. The variation is 2 degrees west. The airfield elevation is 202 feet, and the threshold elevation is 195 feet. The MSA — Minimum Sector Altitude — is 25 nautical miles from the ARP, the Aerodrome Reference Point. The frequencies: ATIS is 136.525. Approach is 126.825, 118.950, and 129.025. Tower is 124.225 and 134.225, with 121.800 for GMC — Ground Movement Control. The radar frequency for this SRA is 126.825. So to tie it all together: an SRA is a non-precision radar approach. The controller gives you advisory heights at each range, you fly the published descent profile, and you must have the runway in sight by the RTR — the radar termination range — or you go around on the missed approach, climbing straight ahead to 3000 feet.