What Does a Plane Go Through Before It Can Fly?

by Terry Ward 
Posted Aug 17th 2010 05:33 PMUpdated Aug 17th 2010 05:35 PM




Rest easy in your window seat -- your plane has been tested and tested ... and tested

Anyone who's sat in a window seat and watched an airplane's wing shake through turbulence like a leaf on a tree has surely wondered: Just what does a new airplane have to go through before it can be certified safe to carry passengers?

All airline industry eyes have been on Boeing as of late, as the Chicago-based aircraft manufacturer tests its new airplane design, the 787 Dreamliner -- a super-efficient aircraft made from composite materials that Boeing says will bring big-jet ranges to mid-size airplanes. (The plane will carry 210 to 250 passengers on trips up to 8,200 nautical miles.)

But long before that airplane will be shipped off to the clients who have already placed their orders, among them United Airlines and Royal Jordanian, there's an incredibly long list of tests to be done.

According to an FAA statement, the federal agency "sets the standards for the certification and continued safety of all aviation products. For an airplane, the agency outlines the requirements the manufacturers have to meet for the structure, materials, and all components in the airplane. The manufacturer must demonstrate through testing or with data that the product meets the government's standards."

On top of what the government requires, manufacturers add their own testing to new-design airplanes like the Dreamliner, according to Todd Sigler, Assistant Vice President of Civil Aviation for the Aerospace Industries Association, which represents the nation's leading manufacturers of commercial, military and other aircraft. "The individual manufacturers have gone above and beyond those [FAA] rules and in many cases, that's based simply on their experience or knowledge of how the airplane will be used," says Sigler. "The FAA's requirements aren't a low standard by any means, but they're set to have applicability to a broad number of products."

And today's airplanes, says Sigler, get wrung out from "nose to tail and wing tip to wing tip" during testing to ensure they can encounter all types of situations during service and remain undamaged.

"They [airplanes] have to be able to show their tolerance to levels of in-flight icing encounters, cold weather testing, hot weather testing," he says. "The things they test for certainly aren't way out in left field, like this will never happen, but they [manufacturers] take it to another level of severity."

Frank Santoni, chief pilot of commercial planes for Boeing Test & Evaluation -- which evaluates all of the company's products -- is one such individual testing the limits of his manufacturer's planes, including the new 787 Dreamliner.

For Santoni and his staff of around 50 test pilots, takeoffs that lead to the plane's tail striking the runway, stalling mid-air and flying through icy conditions without the de-icers switched on is all in a day's work. On any given day, Santoni and his team of about 50 test pilots at Boeing might find themselves in the cockpit of a 747, 777 or the Dreamliner performing maneuvers the rest of us would deem insane.

"As a passenger, it's a pretty benign environment [aboard a commercial flight]," says Santoni. "You fly from point A to B, staying within a normal flight envelope.

"We have to test out beyond that, where the airplane may experience that once or twice in a lifetime event," he says. "We have to make sure it's okay out there."

And the process of testing, says Santoni, is a highly choreographed dance. "We have in the order of thousands of test conditions that we do to certify airplanes," he says, adding that the test program is usually talked about in terms of how many hours the newly designed plane has flown during tests.

To date, the five 787 Dreamliner airplanes currently in the testing phase have flown over 1,300 flight hours. And while there is no standard amount of test hours for new planes, according to experts, past aircrafts have averaged anywhere between . 1,800 and 3,300 hours before getting certified.

Santoni takes us through some of the most interesting and exciting tests a new plane endures before it meets manufacturer standards and gets FAA certification:

Flutter Testing
One of the first ways a newly designed plane is put to test in-flight comes via flutter testing. To understand the concept of flutter and how it affects a plane's structure, says Santoni, imagine an opera singer singing at a very high pitch with the ability to shatter crystal. When an airplane surface vibrates very rapidly [like the crystal glass] it can lead to damages, and flutter has been named as a cause in a number of past airplane accidents. "Most of the times [when flutter is seen], this is an at altitude cruising event," says Santoni. "If you have a loose surface, like a door, it could start vibrating and actually damage that surface.

"We have to be sure that airplanes don't have that tendency, because that's not a good thing to happen," says Santoni, who added that test
pilots at Boeing spend several weeks testing new designs for flutter under various conditions -- different loading weights and configurations, different air speeds -- even reaching the maximum speed a plane will ever go to make sure there are no flutter tendencies in the machine.

"When flutter happens, [the test pilot] can definitely feel it," says Santoni. "But we have instrumentation on the airplane that hopefully detects it before." The 787 Dreamliner passed its flutter testing with flying colors. "There was nothing predicted and there was nothing there," said Santoni.


Minimum Unstick Speed Testing
Any passenger who's ever taken off in an airplane and wondered how the tail manages to avoid skidding on the ground as the plane's nose lifts can rest assured -- there's a flight test to address that concern. Minimum unstick speed testing, one of the most interesting in-flight tests, is a way to show "what the minimum speed is that an airplane can take off at," says Santoni. It's also one of the most exciting assignments a test pilot can get, he says, since planes only get to do it once in their lifetimes.

"What we want to find out is that minimum speed to get enough wind over the wing so that the airplane will actually get into the air," says Santoni, explaining that a woodblock tail skid is put on the back of the airplane where it touches the surface of the runway. "When you get close to the speed, you actually pull the nose up and the pilot can feel the tail touch the surface and it vibrates the airplane some, you can actually feel it, and you wait for the airplane to take off."

Once the minimum speed for takeoff has been determined, it is put into the airplane's manual so that pilots will know to take off at higher speeds to avoid the tail striking the runway. And while the idea might sound terrifying to most of us, test pilots "look forward to doing it because it's so unusual," says Santoni. "We practice in simulators before we go; it's a very regimented build up."


Extreme Weather Testing
Airplanes rotate service throughout their lifetimes and can end up anywhere in the world. To prepare for any possible weather conditions, new designs are tested in extreme heat and extreme cold on the ground and in-flight to ensure avionics continue to function and the plane operates as expected.

The 787 Dreamliner has already undergone cold weather testing and is currently being tested in extreme heat conditions in the southern parts of the US, says Santoni. "We're taking it to very extreme examples of heat down at Edwards Air Force Base or in Arizona and other places where we'll test all the components out in extremely hot weather," says Santoni. "There are lots of places where you have delicate equipment and you want to be sure the cooling is adequate in that area. That's probably the most critical part --component cooling and making sure we don't cook some critical instrument some place on the airplane."

Along with extreme heat (temperatures can get up to 120 degrees), the new designs are tested in extreme cold conditions, too, during flight test in places like Fairbanks and Anchorage, AK. "We'll fly in de-icing, we'll take the airplane and deliberately put it into an icing environment where we'll ice up the wings and the engines and be sure that it can fly in that kind of weather," says Santoni, adding that the Seattle area is one of the best places to test for icing.

"We try to put it in as many critical environments as we can, so we know it will be good anywhere, because the airplane could wind up anywhere," he says.


Maximum Brake Energy Testing
Imagine an airliner fully loaded with passengers, cargo and enough fuel to get it across the Pacific. It's screaming down the runway for takeoff -- when suddenly it's forced to stop. The test to ensure the airplane's brakes can handle sudden braking at high speeds when loaded with maximum weight is called maximum brake energy testing, and Santoni counts it among the most exciting tests to perform as a pilot.

"We load the airplane up to its heaviest weight with fuel and weights that we put in the cargo bay -- up to its maximum weight," he explains. "And you get to a point at the end of the runway, at full power -- a very high speed that you calculate is the maximum speed the brakes can take -- then the pilot applies full brakes and holds them until the airplane stops." Speeds during this test normally reach about 200 miles per hour before the brakes are applied. "By the time the airplane stops, the brakes are glowing red," says Santoni, "There's thousands of degrees of heat in the brakes, and you get to see that it works."


Ultimate Load Wing and Fuselage Bending Test
This test on the amount of load the airplane's frame can support without breaking is one of the more interesting, ground-based tests that new designs endure. When the Dreamliner was recently put to the test which all newly designed planes undergo, the goal was to demonstrate that the airplane's all-composite wings could support 150 percent -- or one a half times -- the maximum load they would ever be expected to encounter during an entire lifetime of flying.

During the test, an infrastructure framed around the plane holds it in place and provides a counterbalance system; the fuselage is pressurized to 150 percent its normal operating pressure. Next, hydraulic actuators incrementally apply a series of loads, bending the wing upwards while simultaneously pulling down on the fuselage to counteract the upbending of the wing.

Watching the process is like watching an enormous machine perform some kind of mechanical yoga. After 120 percent of the test load is reached, the data is assessed before pushing the airplane to 150 percent to ensure it meets the design objective. When the 787 Dreamliner passed this crucial test in early April, applause broke out in the control room.


Stall Speed Testing
It's vital for aircraft manufacturers to know the speeds at which an airplane will stall so that pilots flying the aircraft in commercial service will never get there, says Santoni. Stall speed testing is another in-flight test the 787 Dreamliner and other new aircraft undergo. For a newly designed airplane, hundreds of stall tests are carried out at different speeds and with different weights to make sure the airplane characteristics are good, says Santoni.

"You actually slow the airplane down in flight, so slow that the wing stops flying and that's called a stall -- where you don't have enough air on the wing to produce lift and then the airplane will cease flying," he explains.

If you do this with the wing "clean," [with the flaps up and in cruise position], says Santoni, "you get a lot of natural buffet on the wings so the airplane shakes pretty dramatically -- and that lets the pilot know yeah, you're stalling and shouldn't be there."

Sounds exciting, doesn't it? These tests and many more are part of a day's work for the pilots who work hard to ensure that their airplanes are as safe as possible before the first passenger boards.

Filed Under: Air Travel

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Anne Marie

The author needs a biennial grammar and vocab review!

August 23 2010 at 11:27 PM Report abuse rate up rate down Reply

Since when is Pratt & Whitney Canadian?

August 23 2010 at 10:22 PM Report abuse rate up rate down Reply

the B-787 is lighter using high tech composites,its two engines are very good in fuel consumption .the airplane is lighter and can carry greater payload and the range increases dramatically.

August 23 2010 at 7:11 PM Report abuse rate up rate down Reply
joel morales-cerda

i think it was beter before airplanes & prefer to travel using some other kinds of locomotion...

August 23 2010 at 2:02 PM Report abuse rate up rate down Reply

I do not fly often, but have always felt safe in a Boeing. Airbus, now there I get concerned as it seems one crashes not too long before I fly.

August 23 2010 at 1:53 PM Report abuse rate up rate down Reply
Midnight Flyer

When one looks back in the last decade there appears to be a pattern of accidents that are peculiar to composite airliners. Specifically the tail assembly. I can recall several tragic crashes that involved the tail literally coming off.

I believe these were with the AIRBUS, which, if I am not mistaken, has a mostly composite (plastic) tail. The one that happened on takeoff from JFK seemed to involve the application of full rudder, perhaps to correct yaw from an engine failure. I'm not sure.

In any case, I never heard of the tail coming off of a B-747, which has a metal tail assembly.

Hmmmm. Perhaps these composites are lighter, cheaper and easier to work with than metal, but are they safer? Is there a structural fatigue problem with time and use?

August 23 2010 at 1:49 PM Report abuse rate up rate down Reply

Airplanes are by far the most throughly engineered machines you will ever ride in. If you knew the amount of design, testing, and preventative maintenance that went into these things, you'd shut up and count your blessings. Know what scares me more? All of you idiots who neglect your cars and then share the road with me. Bald tires, worn brake pads, neglected oil changes...

August 23 2010 at 1:47 PM Report abuse rate up rate down Reply
Gene Holdgreve

Well I am not a test pilot,just a former business travler with hundreds of flights under my belt and I would like to share a few experiences with you.

My first flight was on a Delta DC3 which landed on a grass strip in Richmond In. This was a scheduled stop with new passenges boarding from a small building that looked like a two hole out house. We bounced down the runway on takeoff to our next destination, FT.Wayne In. No problems,just a normal flight for that period of air travel.

I also remember flying out of San Francisco when the tail of the plan on takeoff struck the runway and numerous Oxygen masks deployed. No this was not a test flight.

I also remember departing Chicago to London a very full flight when the 747 did not have sufficient air speed to take off. The pilot slammed on the brakes and we stopped at the grassey edge of the runway. The plane returned to the takeoff end of the field starting as far back as the plane could, the pilot reved up the engines with the brakes on and away we went to just clear the grass and into the air. this was not a test flight either.

On another 747 Flt to London we hit major turbulance and the ceiling panels near the tail section fell on top of the passanger seats and I could see up into the tail of the plane. No one was injured as it was not a full flight.
Not a test flight.

I also remember flying into Ft.Wayne In. in a DC3 in January and the runway was covered with ice. We hit the runway at about a 30 degree angle and I thought the plane would crash however, the the runway was so icy that the plane just slid sidways down the runway for a rather long distance. All flights were canceled at that point and passengers going on to Toledp Oh were put on a bus.

I have other stories to tell but I still fly and will be heading out on another flight this week.

Oh yes I remember fire flying from the engine of a prop plane, Loose rivets rotating in the wing of a 737. Oil flying out of a 737 jet engine in flignt. Landing in Clevland Oh. in a storm when all the runway lights went out just as we were approching the runway, baggage falling from the overhead compartments
onto passanges due to turblance. And so it goes with flighing.

Have a nice flight.

August 23 2010 at 1:35 PM Report abuse rate up rate down Reply

I don't know how much those test pilots make, but there wouldn't be enough money for me to do something like that.

August 23 2010 at 1:33 PM Report abuse rate up rate down Reply

All this testing, but for the person taking a trip, the big problem will be how do they herd this large group of people onto that metal tube. Where there will be tight seats, no place to store anything, and every one will have all kinds of carry on.
Now it takes for ever to load a plane but with 250 people you will spend hours waiting in line, and if you are one of the first on, you will spend hours sitting in that chair while every one pushes on and try to put something in the over head bin.
No thank you, I don't care how well it was tested, my days flying around the country were done when flying was fun and enjoyable. They served nice meal, everyone treated you well. You could move around and they did not charge you for breathing. People dressed up like they were going someplace besides the gym.

August 23 2010 at 1:31 PM Report abuse rate up rate down Reply
2 replies to Jack's comment

Yeah, definitely glad those days are gone. Flying sounds like it used to be expensive and snobby. I'm sorry if my shorts and T-Shirt offend you, but I dress to be comfortable when I've got a 5 hour ride in one of those hobbit-sized seats. Besides, I'm sleeping on that flight. None of you are interesting enough to talk to, and the mile high club is a myth. The booze is too expensive as it is. All that there is for me to do is close my eyes in Phoenix, and when I open them, I'm in Boston. Best nap ever.

August 23 2010 at 1:41 PM Report abuse rate up rate down Reply

Concerning my last comment and the reply. First place it did not cost more to fly in those days, as a matter of fact it cost less then now. We did not have all the extra fees. You could check free as many bags as you wanted, you did not pay extra for anything on the plane a pellow, blanket. Some flight when they started to show movies would charge extra for the head set, but not all. Booze in most cases was extra, but there were some flight that I was on when it was free. They treated you like a customer, not baggage.
In my days even the Greyhound bus was a better ride than what we get now on the air planes,they had comfortable seats, and room, and a arm rest.
But the trouble now is that the traveling public never had a chance to fly that way.
When the jet first came out it was cheaper to fly first class on a jet than a prop plane.
No air travel will never be like it was, but as an old man you can travel in your bathing suit, sleep all the way to Boston if you have a chance.

August 23 2010 at 4:30 PM Report abuse rate up rate down Reply

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