In August 1961 a crew of Douglas Plane take a look at pilots proved the brand new DC-8’s value by diving it by the pace of sound.
One would anticipate an airplane slated for a file flight try and be prepped and flawless right down to the final rivet, however earlier than it even left the Douglas Plane plant in California the DC-8 chosen for this specific try was not factory-fresh. In an interview with aviation historian Invoice Wasserzieher for a Douglas worker oral historical past mission, flight take a look at engineer Richard H. Edwards recalled, “The evening earlier than, at Lengthy Seaside, any person had dinged the [wing leading-edge] slats they usually didn’t work.” And throughout the preflight verify Edwards broken the trailing-edge flaps, banging one on a flight crew workstand inadvertently left below it.
With out slats and flaps, low-speed dealing with was going to be tough. Fortunately, this crew wasn’t aiming for a low-speed file. Pilot William Magruder informed them, “Properly, we are able to take off with no flaps and the airplane shall be all proper…if we don’t lose an engine.”
Douglas had rather a lot driving on the flight. Over the earlier decade Boeing had nearly locked up the marketplace for army bombers with its B-47 and B-52. Now with Boeing’s new 707 jet airliner (first flown in December 1957), the corporate was looking for to do the identical to the business market. Douglas had gained an enormous head begin within the airliner enterprise with its legendary prewar DC-3, however its new four-jet DC-8 had not flown till six months after the 707 took off.
Magruder had been copilot in 1958 on the DC-8’s maiden flight. As an Air Power take a look at pilot and engineer he had flown all the things from the North American F-86 Sabre and Martin B-57 Canberra to the Douglas C-124 Globemaster II and B-52 Stratofortress. He had flown with Chuck Yeager, the primary man to exceed the pace of sound in degree flight, and Alvin M. “Tex” Johnston, who had famously flown a Boeing 367-80 (707 prototype) by a double barrel roll, earlier than becoming a member of Douglas in 1956. “He was well-known within the business and really articulate,” recalled Edwards, “effectively educated, with quite a lot of new concepts.”
His latest thought was to seize headlines for the DC-8 by making it the primary business airliner to interrupt the sound barrier. “Very sensible,” agreed Edwards, “get it on the market, present the airplane can survive this and never collapse. Boeing won’t ever attempt it [with the 707] as a result of they don’t wish to be second.”
The DC-8 was decidedly subsonic, designed to cruise at 542 mph at 35,000 toes (Mach .82). Douglas put an entire group of engineers to work on the mathematics. Edwards recalled, “They needed to decide the pushover load issue, the dive angle, to make certain they bought to Mach 1.01 at a reasonably excessive altitude, so the airspeed wouldn’t be that prime up there.”
On the designated day, August 21, 1961, Magruder and Edwards had been joined on the Douglas plant in Lengthy Seaside by copilot Paul Patten and flight engineer Joseph Tomich. The plane chosen for the flight was a brand new DC-8-43, no. N9604Z, the a hundred and thirtieth constructed. The Collection 40 was the primary airliner on this planet powered by turbofans, for improved effectivity and fewer noise and smoke.
Resplendent within the crimson and white colours of its new proprietor, Canadian Pacific Air Strains, and emblazoned with its new title, Empress of Montreal, the DC-8 seemed nice with its dinged slats and flaps closed—no one may inform the fowl was barely crippled. “We took off with flaps up,” admitted Edwards, “which is form of a no-no as a result of at takeoff thrust, you possibly can’t management the airplane if it loses an engine with flaps up—there’s an interlock on the rudder.”
The take a look at was to be performed about 80 miles to the north, over Askania Monitoring Vary at Edwards Air Power Base within the California desert. On the way in which up the DC-8 rendezvoused with a two-seat North American F-100F Tremendous Sabre digicam ship and a Lockheed F-104 Starfighter chase aircraft (flown by Magruder’s previous good friend Yeager) offered by the USAF Flight Check Center, which additionally provided a climate balloon to confirm pace and atmospheric information. Over the southern tip of Rogers Dry Lake, Magruder leveled out at 50,090 toes, in itself a file for a civil airliner at the moment. “The factor that impressed me essentially the most was the darkish, black sky,” recalled Edwards. “I’d by no means seen something like that.”
From that altitude, the remainder of the flight can be downhill all the way in which. It was Edwards’ job to know once they crossed the magic quantity. “The Mach quantity itself isn’t utilized in a dive as a goal as a result of it’s rather more correct to make use of airspeed,” he defined. “So each thousand toes I’d learn off to Invoice the airspeed on the subsequent altitude. As we had been coming down, I used to be speaking virtually on a regular basis as a result of at a descent price of 500 toes per second, each two seconds we had been 1,000 toes decrease. Looking the window—which I ended doing—it seemed prefer it was straight down.”
Because the airliner neared Mach 1 it compressed the air shifting over it into shock waves, able to tearing a poorly designed plane to items. “At .96 Mach it buffeted for some time,” remembered Edwards, “…and a little bit above .96 it went away.”
However shock waves also can have an effect on management surfaces, to the purpose of lowering and even reversing pilot enter. “I had mounted some cameras in the midst of the airplane, taking pictures out every window,” Edwards recalled. “I needed to catch the chase airplanes on the market, however I by no means noticed the chase airplanes within the photos. Nevertheless it did present the ailerons flapping up because the shock wave left—I believe it was about .97 Mach. They went up about 5 levels, I believe—each side, happily.”
Magruder held the yoke regular as Empress made historical past. “Within the dive, at about 45,000 toes, it went to Mach 1.01 for perhaps 16 seconds,” mentioned Edwards. In truth, at 41,088 toes the DC-8 recorded Mach 1.012, 660.6 mph at that altitude. By then Magruder was already beginning to pull out, however as Edwards recalled, “The restoration was a little bit scary.”
When Magruder eased again on the yoke to tug out of the dive, the aircraft barely responded. The elevators, not designed to function at such pace, couldn’t overcome the supersonic airflow. The DC-8 was uncontrolled, hurtling earthward at simply over Mach 1, and in lower than a minute would influence the desert flooring…until it tore aside in midair first.
“Properly, I’ll use the stabilizer,” mentioned Magruder. Apart from the elevators on their trailing edges, the DC-8’s horizontal tailplanes (additionally referred to as stabilators) may rotate as one piece—not less than, at subsonic speeds. At 39,614 toes the DC-8 hit a most true airspeed of 662.5 mph.
“The stabilizer wouldn’t run….due to the load,” recalled Edwards. Within the high-speed pullout, with the airliner ever so barely nose-up to the wind, the motor controlling the tailplane angle actually couldn’t overcome the air strain below the tail.
“What [Magruder] did, as a result of he was sensible, is one thing that no different pilot would do,” mentioned Edwards. “He pushed over into the dive extra, which relieved the load on the stabilizer.”
It was unconventional considering—enhance the dive price to tug out of a dive? However as quickly as Magruder stopped attempting to tug out, the airliner “straightened out” into the wind, and the decreased air strain allowed the tailplane motor to perform and the stabilators to chunk into the airflow. They “recovered at about 35,000 toes,” Edwards famous, little doubt with a way of aid.
In the midst of the dive the DC-8 had coated virtually 15 miles, to the southern tip of Rosamond Dry Lake. “We had been all smiles,” mentioned Edwards. “We weren’t frightened, however we had been roughly pleased that we had bought there.”
In simply that one flight, Empress of Montreal had set altitude, payload and pace data for business transport plane. The pace file stood till damaged by a Soviet Tupolev Tu-144 SST in June 1969. Every crewman acquired a $1,000 bonus from Douglas, and the Society for Experimental Check Pilots awarded Magruder the Iven C. Kincheloe Trophy for excellent skilled accomplishment in flight testing.
Canadian Pacific took supply of Empress of Montreal that November. With a small plaque on the ahead bulkhead testifying to its place in historical past, it served for nearly 20 years, logging 24,268 flights for a complete of 70,567 hours within the air. In Might 1981 it was offered, and at Opa Locka Municipal Airport north of Miami, Fla., scrapped. It by no means broke the sound barrier once more.
The Fourth SST
DC-8 no. N9604Z was the primary airliner to exceed Mach 1, however not the final. The Concorde and Tu-144 made supersonic passenger flight appear routine (not less than, till a collection of crashes and financial issues brought about their retirement). In the present day most business airplanes just like the Boeing 787 and Airbus A350 cruise round Mach 0.85 to 0.89, whereas smaller company jets from Cessna, Gulfstream and Bombardier routinely cruise above Mach 0.90. It’s not unparalleled, nonetheless, for subsonic airliners to exceed Mach 1 (761 mph at sea degree), not less than by way of floor pace.
In February 2018 a Norwegian Air 787-9 heading from New York to London caught a experience on the jet stream over the Atlantic. Dreamliners had beforehand reached 776 mph with a tailwind, however this one made the crossing in 5 hours and 9 minutes, topping out at 799 mph. And a yr later, a Virgin Atlantic 787-9 out of Los Angeles on its solution to London additionally caught the jet stream 35,000 toes over Pennsylvania, reaching a floor pace of 801 mph. As a result of the high-speed wind was carrying the jets like boats on a river, these airplanes didn’t exceed Mach 1 as measured by native airspeed. A minimum of one different non-SST airliner, nonetheless, did break the pace of sound…although not deliberately.
In April 1979 TWA Flight 841, a Boeing 727-31 en route from New York Metropolis to Minneapolis-Saint Paul, Minn., deployed the no. 7 modern slat on its starboard wing whereas cruising at Mach .816, 39,000 toes over Saginaw, Mich. Slats being low-speed, high-lift units, the ensuing asymmetrical elevate and drag instantly threw the airliner right into a starboard roll. It entered into an uncontrolled spiral dive and plunged about 6 miles in 63 seconds, in accordance with the flight recorder doing two full 360-degree rolls and breaking the sound barrier within the course of. At that velocity the wind tore off the uncovered slat, the captain dropped the touchdown gear to place most drag on the airframe and the crew regained management with about 8,000 toes to spare. They made a profitable emergency touchdown in Detroit.
Regardless of broken touchdown gear, elements of flaps and wing spoilers lacking and a bunch of different harm together with a cracked cabin window, the passengers and crew suffered solely minor accidents. The plane was returned to service a month later. A Nationwide Transportation Security Board investigation attributed the incident to incorrect operation of the slats by the crew. (A rumor had circulated that barely deploying slats and flaps at cruising pace elevated the 727’s elevate with no enhance in drag, yielding higher gasoline effectivity. In accordance with the NTSB, the crew had deployed all of the slats, however attributable to air loading no. 7 did not retract.) The crew strongly denied wrongdoing, stating seven earlier incidents of single-slat extensions by 727s.
Frequent contributor Don Hollway final wrote for us about Basic Curtis LeMay within the November 2021 difficulty. His most up-to-date guide, The Final Viking, was launched in September 2021 to vital acclaim. Additional studying: Douglas DC-8, by Terry Waddington.
This characteristic initially appeared within the March 2022 difficulty of Aviation Historical past. Don’t miss a difficulty Subscribe!