Pardon my basic graphics but think about what the break is designed to do. First, it is designed to achieve a safe separation for the formation members to then perform individual landings. Second, we are still in a formation, and in our world of airshows, it gives us a chance to show off a little to the crowd that we can affect spacing while visually looking as if we are each doing it exactly the same way. Third, and most important for safety, it allows us to achieve the lateral offset needed to safely perform the final turn. Let’s look at each of these factors in turn. The first question to ask is how many seconds do we need between each aircraft before commencing the break? Well, that depends on the aircraft, its performance, and how much spacing you want at the threshold between aircraft. For a Yak-52 or a CJ-6 flight flying at 120-125 KIAS, you are moving across the ground (no wind) at 200 ft/sec. If you want 1000 ft separation then use a 5 second break. For a flight of T-28s flying at say 180 KIAS, you’re moving at 300 ft/sec. If you allow that you’ll use more runway and therefore need more spacing, a 5 second break would give you 1500 ft separation at the threshold. In my years in the USAF, we used 3000 ft as a standard runway separation between flight members on landing. Remember we had the luxury of 8-10,000 ft runways. Of course a T-38 flies final at 155 KIAS plus fuel additive and lands at 130 KIAS plus additive. And some aircraft are even faster! The assumption here is that you are using alternating sides of the runway. If the runway is not wide enough for that, then double the separation! I fly a lot of L-39s. With a touchdown speed of 90-100 KIAS, 2000 ft of separation is comfortable. For an L-39, your initial speed can be anywhere from 200-250 KIAS. At 240 KIAS, you’re moving across the ground at 400 ft/sec. A 5 second break again will give you the required 2000 ft of separation. Last point about timing of the separation: you’re trying to achieve a specific separation at the threshold. What if the airplane in front of you blows a tire, or loses a brake, or has a landing gear collapse? Your separation should allow you to stop prior to the aircraft ahead, or allow you to go around. A Yak or CJ can stop in about 1000-1300 ft if everything is done perfectly. An L-39 can stop in about 1800-2800 ft depending on density altitude. The bottom line is for the flight leader to specify a spacing that satisfies his sense of safe separation based on a worst-case scenario. The second point was how we look at airshows. If we are precise in our timing, and use the exact same bank angle and G-force, then the spacing should be good. The leader should also brief the power settings or airspeeds to use on the downwind, final turn, and final. This helps to keep things symmetrical. If you find yourself closing on a flight member ahead of you, correct your spacing by going wider, not vertical. The crowd sees vertical movement as a sloppy position whereas they can’t see that you’ve gone just a little bit wider. The last point, and perhaps the most important one as it relates to what happened in Texas, is the question of how much lateral spacing do you need, and what bank angle/G-force will achieve it? For a Yak-52 or CJ-6 at 1000 ft AGL, on a no-wind day, 45 degrees of bank and 1.5 Gs will give you perfect lateral spacing to the runway. Visually, the wing should overlap the runway about 3/4ths of the way out to the wingtip. For an L-39 flying initial at 1500 ft AGL and 200-220 KIAS, 60 degrees of bank and 2 Gs will roll you out perfectly with the wingtip fuel tank superimposed on the runway. If there is a strong crosswind the flight leader must compensate, pitching out wider for an overshooting wind, or perhaps a little closer for an undershooting wind. The accident in Texas occurred on a day with a very strong overshooting wind in the final turn. We all know that base turn stalls are a big killer in general aviation. It is so easy, especially in an overshooting wind, to misjudge your ground speed. We’ve all seen how a pilot tries to salvage an overshooting final. They increase bank angle and Gs. When the nose starts to rise, they compensate with bottom rudder. So here they are with low speed, power and altitude, and cross controls. The wings stall unequally and a spin results with not enough altitude to recover. This may have been the problem in Texas. This brings up a related point: do you fly a square pattern or a continuous final turn in a tandem-seat aircraft and why? First off, in a tandem, there is no need to roll out just to look cross-cockpit. You can see equally well in both directions. In some types, the outside wing can block your view of the extended final but not in all types. Many jet fighter cockpits are placed well in front of the wings. By flying a continuous turn on base vs. a square pattern, you actually use a little more airspace to allow you to lose your altitude while keeping your airspeed under control. Remember, most of us fly single-engine aircraft so our patterns are tight in case of engine failure. The last and most important point about a symmetrical final turn is about being able to judge your turn radius to the final. In a continuous turn, I can recognize earlier in the final turn what the wind is doing to my radius. If I need to use a little more or less bank and G, I’d rather make that correction at a higher altitude and with less control input required. In fact, when I come off of the “perch” and start my final turn, I look abeam my position for a ground reference on the extended runway centerline. I plan every overhead pattern to be at that point between 250-500 ft AGL depending on the type of aircraft and how long a final I’m planning. Treat that extended point on final as a decision point just like on an instrument approach. Better to make an early decision to go around than to try to salvage a poorly executed approach. Ok, let’s talk through a couple of examples. In the Yak community, I brief a 5 second break, with everyone pulling 1.5Gs at 45 degrees of bank. I know. Everyone wants to be steeper and pull more aggressively for the crowd. But it’s the above parameters which will give you the spacing you want. It’s hard with different types to set one power setting for all but I tell my flight members to fly the downwind at 100 KIAS, put the gear down precisely abeam the “numbers”, put landing flaps down when the runway is 45 degrees off your shoulder, and start the final turn immediately. I fly the base at 90-100 KIAS, and 90 KIAS on final. If landing distance is critical, then I fly final at 80 KIAS and use increased spacing in the break. If you start your final turn when the preceding aircraft is exactly halfway through his, he’ll be crossing the threshold as you roll out on final and spacing will be perfect. With an L-39, I don’t usually have the 200 KIAS restriction in Class D Airspace to deal with but approximately 90% N1 gives you 200-220 KIAS on initial. That power setting keeps everyone out of the 86-89% N1 range for stage 3 surge bleed valve operation. A 5 second break works perfect, and I brief each formation member to set 80% N1 and use 60 degrees of bank and 2 Gs. You will bleed off the 40 knots in the turn, allowing you to put the gear down below 180 KIAS abeam the runway threshold, and flaps 25 at the 45 point below 165 KIAS. I fly the final turn at 140 KIAS and final at 120 KIAS. I put flaps 44 down halfway through the final turn unless some unusual situation makes me think I need it a little sooner or later. All the rest applies with regards spacing. Obviously, a faster airplane requires a bigger pattern and longer final but the concept of how to achieve the spacing is identical. Also, you’ll lose about 1/3rd of your altitude halfway through the turn, the second 1/3rd in the second half, and the rest on final. Each type aircraft might bring its own set of limitations or special needs but this works for most. I’ve flown A-10s, F-15s, T-38s, L-29 & 39, and even a MIG. It works for all of them. If nothing else, I hope this discussion of pattern procedures and techniques generates further discussion among your flying partners. We don’t have to make the same mistakes as those before us. Through practice and professional discipline, the overhead pattern, whether in single-ship or formation, can be performed precisely and safely. Fly safe and always remember to “check six!” Richard Mongoose Hess [Featured Article Archive] |