Mysteries of Flight: The Downwind Turn

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The Theory

The purported hazard of the downwind turn is one of the most controversial topics in all of aviation. Despite it being widely debated for many decades, it maintains a hold on the popular pilot imagination because its potential consequences are dire.

Here’s the concept. We all know that airplanes fly because of what we call the relative wind through which our planes’ wings move, or vice versa. There doesn’t have to be any ground speed at all for a wing to fly. If you’ve been at an airport during a period of very high winds, you might have seen airplanes chained to the ground rising up and flying. When the wind suddenly stops, obviously the plane settles to the ground.

But does this same phenomenon take effect when a plane is airborne? Not really. We do see this effect on takeoff, where downwind takeoffs require much more runway than upwind ones. But all of these effects are in relation to the ground, not the air.

Take a hypothetical plane—let’s say a Skyhawk—and let’s imagine it flying into the wind. For the sake of the math, let’s say it’s doing 100 knots indicated and the wind is 10 knots on the nose. Now turn the airplane in the opposite direction so that the wind is behind you. You’ve now got 20 knots on the tail. The theory of the downwind turn holds that the plane has lost not just 10 knots of airspeed but 20, as it is not only losing the 10 on the nose but it’s gaining 10 on the tail. 100 minus 20 equals 80 knots, which is no big deal. A 172 will fly just fine at 80 knots.

But if you’re low to the ground, will that presumed loss of airspeed cause the plane to sink as it regains its normal, desired speed? And if you’re close to the ground when you execute this turn, could that mean a risk of colliding with terrain?

It seems like a real risk, so pilots who subscribe to the theory of the downwind turn advise their fellow pilots to make such turns with great caution.

The Issue

The theory of the downwind turn has many problems, but looking at it using a more extreme example might be illustrative. Let’s take that same Skyhawk heading into the wind but this time instead of a 10-knot headwind, let’s make it a 50-knot wind, something that is rare close to the ground but not unknown. As in the previous example, this Skyhawk turns 180 degrees, so that its heading goes from being directly into the wind to having the wind directly on its tail. That 50-knot headwind just turned into a 50-knot tailwind, so the indicated airspeed goes to…well, zero, right, with the loss of 50 knots of headwind and the addition of 50 knots on the tail. So, the plane falls out of the sky, like the proverbial grand piano dropped from a cliff.

Well, we all know that this doesn’t happen. The plane not only keeps flying, but its indicated airspeed will be unchanged. It doesn’t fall out of the sky and, in fact, if the plane were in IMC, the pilot would be blissfully unaware of the change in the plane’s orientation to the wind, unless they had a readout of ground speed or wind speed to refer to (as many of us do indeed have these days). But why doesn’t it fall out of the sky?

There is a phenomenon that will cause an airplane to fall out of the sky—well, to sink strongly even with no change to the power settings or attitude—and that is known as wind shear. Wind shear is different in that it is an almost immediate change in the relative wind. The most dangerous form of wind shear comes along when there is strong convective activity—a thunderstorm. A plane flying into a 50-knot headwind that suddenly turns into a 10-knot tailwind is indeed in a world of hurt unless the pilot reacts quickly with a big dose of power. Some of the most deadly crashes in aviation history have happened in just such a scenario.

The Truth

The downwind turn is a myth.

Wind shear is not what happens with a downwind turn. When an airplane turns from going into the wind to a downwind direction, it does so not all at once but in an infinitesimally small series of changes. So unless there is wind shear, the airplane maintains equilibrium throughout the turn. That’s it. It’s simply unlike wind shear, where the change in wind is almost instantaneous.

There are theories about why the myth of the downwind turn is so hard to dispel, but the most likely is that it looks like it’s true. Indicated airspeed doesn’t change (after the turn is completed; turns are still turns and add Gs and raise stall speed). So from one direction of flight (upwind) to the next (downwind), there’s no effect at all (disregarding the aerodynamic effects of the turn).

But what does change, and change dramatically, is the ground speed during the downwind turn. If you imagine the change in ground speed when you turn from downwind to final in one standard-rate U-turn, you will see your airplane seem to throw on the brakes. Now reverse that procedure and turn from a strong upwind leg to a downwind landing. Your speed over the ground will not only be much greater but it will look much greater, and you’ll get to the threshold much faster. That sight picture of the plane apparently speeding up (its airspeed is actually unaffected) looks for all the world like what happens when you point the nose down and accelerate in no-wind conditions.

The good thing about the myth of the downwind turn is that so long as pilots believe it, they’re more likely to pay careful attention to their airspeed when they’re close to the ground and especially on low-altitude turns, where an unplanned rendezvous with terra firma is the worst possible outcome of flying down low on a windy day.

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Speech – Amazing is What You Do

Acting Administrator Daniel Elwell
Washington, DC

Remarks as prepared for delivery

Thank you, Paul. Im happy to be here. I want to thank you and Trish for your leadership and for being such great partners.

I also want to thank our controllers for the job you do every day. You safely handle about 45 thousand IFR flights a day over 31 million miles of domestic and international airspace.

To the layperson, this is nothing short of amazing.

But its what you do, every single day.

When it comes to safety and efficiency, you have set an incredibly high bar.

Ill give you a good example.

Last month, controller Tim Martin at Daytona Beach Tower came through for a 20-year old student pilot who was in trouble.

The pilot was flying solo when engine oil sprayed all over his windscreen. He couldnt see anything forward or sideways.

Tim calmed him down, and got him towards the Daytona Beach Airport. Once the aircraft was close to the runway, our tower controllers gave vertical guidance to the radar controller to relay to the aircraft.

Tim and his colleagues worked together to guide this pilot all the way to touchdown, and then let him know how much runway he had left.

When the student landed, he said we had saved his life.

Saves like these remind us that we must always be vigilant. Whether youre in the cockpit, the tower cab or the centerthe calmest, most benign day can turn on a dime into a life and death situation.

This became all too clear after Captain Shultz engine failed on Southwest Flight 1380. Tragically, this event took a life.

But, if not for the calm professionalism and coordination of the flight crew and air traffic controllers, it could have been much worse.

We had gone 9 years and 3 months without a commercial passenger fatality. But that tragedy reminds us that ensuring safety is a never-ending task.

The FAA and NATCA are doing everything possible to drive down safety risk. We have to continue to collect and share safety data identify and target the highest risk areas and work with our stakeholders to address the problems.

Over the past 10 years, FAA controllers have submitted more than 147,000 ATSAP reports. From these reports, we have put in place 181 corrective actions.

Thats 181 more ways to extend the safety margin so that accidents dont happen!

Let me give you some examples.

A controller at Albany Tower reported that trees were obstructing the view of Runway 28.

Thats a potential trigger for runway incursions.

ATSAPs Event Review Committee shared the report and coordinated a full Obstruction Evaluation. And following that, we put out a contract to remove or trim the trees from public and private property.

Employees at Kansas City Center also submitted ATSAP reports indicating problems with some frequencies for Kirksville, Missouri.

There were scratchy readbacks, numerous repeats, and missed calls. The frequencies had become useless on main and standby.

This is a bad thing all the way around. It could lead to miscommunication between controllers and pilots.

This could result in increased workload, distractions, and the potential for airspace and separation issues.

Technical Operations looked for causes and solutions, and last year they implemented a series of mitigations to solve the problem.

It was the ATSAP reports that really elevated the issues, so they could get the attention they needed.

None of that happens without you leaning forward. ATSAP turns up things that otherwise would have gone unattended to. Were as safe as we are because we make sure we get things right, and when theyre not, we fix them. Together.

As I said, this is what we do.

And its the same approach we need to take as drones come into the field.

This industry is rapidly evolving, and the FAA must stay a step ahead.

Our goal is to ensure safety while enabling innovation.

We could be looking at 3.5 million drones by 2021. As part of this effort, we have to ensure the safety of other aircraft and people and property on the ground, while safeguarding the needs of traditional airspace users.

Earlier this month, Secretary Elaine Chao announced the ten selectees that will take part in the FAAs UAS Integration Pilot Program.

These sites are going to change how we look at aviation. Were well familiar with border patrol, package delivery, and emergency response. Were just used to having someone sitting up front to do it.

Its a new day.

Over the next two and half years, the selectees will collect drone data on night operations, flights over people and beyond the pilots line of sight, and on detect-and-avoid technology.

For specific drone flights, they will be able get expedited approval for airspace authorizations. In turn, they will give us the data that will inform our regulations on drones.

Last month, the FAA announced a national beta test of a new automation tool called LAANC.

Were at the mercy of acronyms. LAANC is the Low Altitude Authorization and Notification Capability.

LAANC is designed specifically to expedite requests by drone users to operate in controlled airspace near airports.

At early prototype locations, LAANC has cut the average approval time from three months to less than one minute.

As part of the beta test, over the next six months, the agency will be rolling out LAANC to nearly 300 air traffic facilities and about 500 airports.

We look forward to seeing the results.

Through the UAS Pilot, LAANC and the other efforts were making, the U.S. will continue to lead the world in safe drone integration.

None of this happens without you, and were going to hire more than 5,000 controllers in the next five years, to make sure were in a place to succeed.

Again this year, our hiring has been going very well. As of last week, we were at 82 percent of our hiring goal of 1701. This will be the third year in a row we have exceeded our goal.

Our largest staffing challenge is at New York TRACON. As you know, N90 is one of the worlds busiest and most complex RADAR facilities.

Over the past year, weve posted two announcements for experienced applicants to be assigned to N90. The ATO is providing the selected applicants with more intense simulator training that comes close to matching the real traffic there.

We have also taken steps to enhance Academy training. Its called Ten Eleven Twelve Radar Assessment, or TETRA. In the future, we will employ this training for new hires at N90 and other large complex RADAR facilities.

Thanks to NATCAs advocacy, there was a change in the law allowing us to post an announcement to hire applicants with no experience within a local commuting area.

We plan to post this announcement on June 19th, preceding an all-sources announcement scheduled for June 27th.

And whether its hiring, or any other important investment we make at the agency, stable funding is an important issue.

We must have a funding stream thats sustainable and matches what were trying to accomplish.

We were pleased that the House passed a five-year FAA reauthorization bill last month. But it certainly didnt play out the way we had hoped.

While we understand the political dynamics that prompted Chairman Shuster to remove the air traffic control reform title from the bill, we all agree that the status quo has not provided a stable, predictable funding stream to operate and modernize the NAS.

The stop-and-go funding has delayed needed system improvements. It makes planning for modernization projects difficult and more expensive.

And the 2013 sequestration forced us to suspend controller hiring and shutter the Academy for a year.

The pending bills are far from perfect, but Im committed to ensuring that you get the resources you need to continue delivering the level of service that the American people expect.

Under the leadership of Chairman Shuster and Chairman Thune, Im confident that a long-term bill will be enacted this year.

As controllers, your professionalism and teamwork are major reasons for aviations historic safety record.

I mentioned Flight 1380 earlier. When the pilot told Corey Davids, controller at New York center, they had to make an emergency landing, Cory and nine other controllers cleared the airspace so the plane could land in Philadelphia, as soon as possible.

Otherwise, the tragedy could have been much, much worse.

People who read or watched this story thought it was amazing.

But, I think Cory put it best when he said, We have thousands of controllers around the country that go in everyday, do their job, leave, and no one hears anything about anything.

Corys right. This is simply what you do. This is why FAA remains the gold standard around the world.

I look forward to working with you to keep it that way.

The GE Advanced Turboprop Engine Finally Has A Proper Name!

Perhaps it’s because GE has finally tired of the good nature ribbing it’s endured from the aviation media or maybe it’s because it’s tired of explaining to friends it bumped into at the park that they’re still working out what to call their three-year-old, but for whatever reason, GE has finally settled on a name for its clean-sheet turboprop engine that will power the emerging Cessna Denali single-engine turboprop. Drumroll please… it’s “Catalyst.”

The GE Catalyst Engine
GE has named it’s clean-sheet turboprop engine, “Catalyst.”

It’s a good name for it, too, for an engine that will enter service in a couple of years as the leader in just about every performance and reliability standard. The 1,240 shp engine is the first of a family of such engines that will range from 1,000 to 1,600 shp. The engine has an industry best pressure ratio of 16:1, which allows the engine to burn 20 percent less Jet-A and to deliver a higher percentage of power at cruise. Its 4,000 TBO will also be best in the biz by a third.

How does it do it? In part, it’s because of its innovative components that GE makes with an advanced form of 3D printing called “additive manufacturing.” On the Catalyst engine, GE has replaced 855 conventional parts with just 12 printed parts. According to GE, these include sumps, bearing housings, heat exchangers and exhaust case housings. The elimination of parts means fewer hot spots for failure and lower weight. GE says that additive parts cut the weigh of the engine by 5 percent and increase its specific fuel consumption by 1 percent.

The engine is currently undergoing testing at GE’s facilities in Prague, Czech Republic, where it has been run for 60 hours. The company is assembling the second Catalyst engine now. Textron Aviation plans to make the first delivery of its Denali turboprop in 2020. By then, GE estimates the Catalyst will have amassed more than 2,000 hours of testing.

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Bye Aerospace Taps Siemens for Motor on Sun Flyer 2

Olaf Otto (left) and George Bye
Olaf Otto (on left) of Siemens, and George Bye of Bye Aerospace.

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Bye Aerospace has partnered with Siemens for future development of the company’s Sun Flyer 2. Siemens will provide the electric propulsion motor and inverter for the plane.

“Members of the Siemens team have already been participating in development and certification meetings with the FAA, and we will be making future announcements about progress with the Sun Flyer 2’s flight test program,” George Bye, CEO of Bye Aerospace, said in a press release.

The Sun Flyer family of aircraft, which includes the 2-seat Sun Flyer 2 and 4-seat Sun Flyer 4, intends to be the first FAA-certified, U.S.-sponsored, all-electric airplanes for the flight training and general aviation markets. To accommodate the aircraft’s needs it will be outfitted with the SP70D motor from Siemens with a 90kW peak and a continuous rating of 70kW.

“The Siemens SP70D motor has been specifically designed for the needs of 2-seater flight trainers,” said Dr. Frank Anton, executive vice President and head of eAircraft, Siemens. “We know that safety, performance and cost of electric propulsion in the flight training market will be game changing and we are proud to partner on the Sun Flyer family of aircraft.”

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Plane Facts: Oldest

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Photo by By Håkan Dahlström – CC BY 2/0/Flickr

Oldest flyable aircraft: Two Blériot XIs

Year built: 1909

Located at: The Shuttleworth Collection (UK) and the Old Rhinebeck Aerodrome (U.S.)

Oldest person to get a pilot’s license: Lt. Col. (ret.) James Collins Warren

Age at which he received his pilot’s license: 87 6. History: Former navigator with the Tuskegee Airmen

Oldest active pilot in the United States: Ernest Eli Smith, Red Oak, Iowa. 100 years young.

Year Ernie soloed: 1943

Year that he got his ticket: 1946 (after the war)

Oldest continuously operating airport in the United States (and the world): College Park, Maryland

Opened: 1909

College Park’s first flight instructor: Wilbur Wright

Longest continuously produced civilian aircraft: Beechcraft Bonanza

First flight: 1945

Canada’s longest continuously operated airport: Edmonton/Cooking Lake Airport

First opened: 1926

Canada’s oldest seaplane base: Also Edmonton/Cooking Lake Airport

Longest continuously produced U.S. military plane: Lockheed C-130

First flight: 1954

Longest continuously operated U.S. military plane: Boeing B-52

First flight: 1952

Number built: 744

Last year in production: 1962

Longest helicopter in production: Vertol/Boeing CH-47 Chinook

Production run: 1962-present

Number built: More than 1,200

World’s oldest known A&P mechanic: Azriel Blackman, American Airlines, 92 years old

First year on the job: 1942 (16 years old)

Oldest commercial airport: Flughafen Hamburg (Hamburg, Germany)

Opened: 1911

Oldest active pilot ever recorded (2007): Cole Kugel, Longmont, Colorado

Age at time of last flight: 105 years old

Oldest air traffic control tower, world-wide: Croydon Airport, London

Opened: 1920

Oldest air traffic control tower, U.S.: Cleveland-Hopkins International Airport (originally called Cleveland Municipal Airport), Cleveland, Ohio

Year tower opened: 1930

Oldest commercial airliner still in production: Boeing 737, 1968-present.

Longest-produced turbine civil aircraft: Beechcraft King Air

Production: 1964-present

Oldest aircraft manufacturer: Short Brothers, Belfast, Northern Ireland, 1908-present

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