Jim, I don’t remember that, but with modern FMS/GPS, setting a different electronic glide path above 3 degrees is not a problem. In fact, I proposed a slightly lower glide path for 28L (over the water) and higher glide path for 28R in SFO for the lighter aircraft (B737, etc.) to avoid the wake vortex. but it also did not get any traction. As I said, ATC and airline thinking that is stuck in the past. The question should not be “is it different”? The question should be “is it safe”? This seems like a perfect task for NASA. Michael xxxxxxxxxxxxxxxxxxxxx R. Michael Baiada cell - (303) 521-6047 <mailto:[email protected]> [email protected] From: James Loos via Mifnet <[email protected]> Sent: Saturday, August 16, 2025 08:50 To: [email protected] Cc: James Loos <[email protected]> Subject: [Mifnet 🛰 73649] Re: Wake Vortices Back in the day, when God first invented wake turbulence, our friends at O'Hare came up with the theory ofr the second aircraft on approach being above the turbulence so we could use three miles. The FAA powers that be wouldn't go for it. Don't know if wisdom prevailed later. Cheers Jim Loos On Fri, Aug 15, 2025 at 3:46 PM ATHGroup--- via Mifnet <[email protected] <mailto:[email protected]> > wrote: The following video is a perfect example of airline thinking that is stuck in the past. This Is Why Airplanes Must Wait <https://www.msn.com/en-us/travel/article/this-is-why-airplanes-must-wait-on-the-runway/vi-AA1KwVnL?ocid=msedgntp&pc=LCTS&cvid=cb5bd614231a4508dc942706462068a0&ei=18> On The Runway I wrote the following in 1994 in the Blueprint to FreeFlight study <https://greenlandings.net/wp-content/uploads/2023/08/Blueprint-to-FreeFlight-3-Volume-Set-1994.pdf> that I coauthored with Michael Boyd. Airlines could. Airlines Should. Airlines refuse. While written about arrivals, it also applies to departures. xxxxxxxxxxxxxxxxxxxxxxxxxxx Another important factor limiting today’s final approach segment is wake vortices. This are small areas of circular wind that are generated by the aircraft wing tips. Because of the severity of this circular wind, spacing of aircraft on final approach is elongated, with the largest spacing when a small, light aircraft is following a heavy aircraft (e.g., a Beech 1900 following a B747). Under Free Flight two solutions can be applied to this problem. The first, especially important at the hubs, is for the airline to choreograph their arrivals so that all heavy aircraft arrive to the same runway, one after another. This lowers the separation between aircraft since a heavy aircraft following another heavy aircraft is not as affected by the vortices. This also makes good operational sense, since the largest aircraft have the longest ground turn time, and could be bunched to arrive at the beginning of the operators bank and all depart at the end of the bank. Secondly, the aircraft glide path (or vertical descent path) near the runway can be varied. Since, as a rule of thumb, the vortices travel down and out from the aircraft wingtip at 5 MPH, flying above the preceding aircraft significantly reduces the probability of encountering the vortex. In fact, this is exactly what is being done today by pilots in good weather and is one of the largest factors in VFR runway acceptance rates being 30% to 40% higher than IFR rates. GPS, would be an important part of this solution. Using GPS, smaller aircraft could be put on a higher glide path with a touchdown point farther down the runway. All these technologies exist, the industry needs the political will to demand their implementation. Flow sequencing, on the other hand, is the task of choreographing the arrival stream into an airport, or any area that is restricted (i.e., a single hole in a line of thunderstorms versus a landing runway). The operator should manage the arrival flow to choreograph aircraft sequencing to meet their operational and economic requirements, not the ATM provider's connivance. Because of this, flow sequencing is operationally and financially critical at the hubs. Whether a flow capacity restriction is in place or not, arrival aircraft, especially at a hub, must be sequenced by the user/operator to maximize operational efficiency and meet internal business requirements. Once the sequencing is accomplished, the separation manager's job would be to monitor the flow for separation and merge additional aircraft into the flow as required. The bottom line is that managing the mix of the arrival flow is a function best handled by the airline or operator. Michael xxxxxxxxxxxxxxxxxxxxx R. Michael Baiada cell - (303) 521-6047 <mailto:[email protected]> [email protected] -- Cheers Jim Loos
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