Boeing 727: Groundbreaking tri-jet was the best-selling airliner for 30 years

Boeing has come under fire lately for allegedly failing to meet quality control standards in some of its aircraft, but this isn’t the first time the now-industry giant has fought for survival in the battle for dominance in the domestic airliner market. In the late 1950s, the concept of the jet airliner was still a novelty. Early jets flew side-by-side with “legacy” propeller-driven airliners for quite a few years. Though its 707 was America’s first jet airliner, and defined the standard for international air travel at the time, Boeing was scrambling to meet orders of the 4-engined aircraft when airline companies began clamoring for a more efficient, smaller airliner that could serve smaller airports and fly short- to medium domestic routes. In somewhat of a gamble, rather than try to sell more–but less expensive–jets, Boeing bet on quality and reliability above all else, reasoning that happier airline customers and lower maintenance costs would save airlines loads of cash in the long run.

The result was the remarkable Boeing 727, which would go on to shatter every foreseeable sales record and was so reliable that it (arguably) never suffered a crash that wasn’t caused by pilot error. If you were near airports or flew on any airline from the mid ‘60s through the 1990s, chances are you saw and/or flew in quite a few 727s. Let’s go over some of the reasons this distinctive, narrowbody tri-jet sold so well for so many years.

Development (and ballooning costs) of the Boeing 727

Several airlines had approached Boeing in the late 1950s asking for a jet airliner capable of servicing smaller airports with shorter runways and/or steeper approach/takeoff routes due to mountains or other obstacles. Additionally, a more efficient engine setup than the then-standard four-jet, wing-mounted arrangement would ideally provide sufficient thrust and range while still saving money on fuel costs, lowering ticket prices and boosting travel. 

United Airlines originally requested a four-engine design that would do well at its high-altitude hub in Denver, while American Airlines favored a twin-engine airliner to save fuel. Eastern Air Lines asked for a model with a third engine for its overwater flights to the Caribbean, since at that time twin-engine commercial flights were limited by regulations to routes with one-hour maximum flying distance to any airport. In addition to expanding their flight radius, a third engine would ostensibly allow greater safety if one engine lost power during a flight. After some back-and-forth, all three customers agreed that a tri-jet design would fit their needs if the performance was within projected goals. 

Simple Flying says, “Knowing the potential for massive sales, Boeing was not alone in trying to develop such a jet; competitors Lockheed, Convair, Douglas, de Havilland, and the British Aircraft Corporation were all working on [an airliner] that could take off and land on runways shorter than 5,000 feet.”

Boeing’s project leader for the 727 was Jack Steiner, and his group began with the universally liked 707’s front fuselage and cabin section, but redesigned the entire aircraft from the wing rearward to the tail. The tailsection was strengthened, since all the thrust would be coming from its 3 rear-mounted engines: 2 engines mounted to the fuselage, one per side, and a central engine exiting the center of the tailsection, with an S-shaped intake duct, having its forward opening at the base of a steeply swept vertical stabilizer. With the engines placed where the horizontal stabilizers typically would go, the 727’s horizontal stabilizers were moved to the top of the vertical stabilizer in a distinctive T-tail arrangement. Moving the engines from the wings to the tail area freed up a lot of space under the airplane, and the lower section of the 727 was made intentionally shallow to allow easy access to cargo holds and service connections from ground level. Designers also added an integral staircase that could be lowered underneath the tail, which was an additional boon to smaller airports since passengers could board and deplane without stair trucks or movable ramps.

Crucially, the tri-jet arrangement with all of the engines located aft of the wing allowed a completely new wing design, with excellent low-speed flying characteristics but also efficient high-speed performance at altitude. The main innovation here was the 727’s complicated system of extendable leading-edge slats and trailing-edge, triple-slotted Fowler flaps that together transformed the fast, steeply swept, .90-Mach capable wing to a high-lift wing that is excellent at low speeds for takeoff and landing. After some initial tweaking, the system proved exceptionally reliable over the aircraft’s service life.

Another 727 innovation that’s near and dear to our hearts at Intergalactic was its gas-turbine Auxiliary Power Unit, or APU. Read our full article on air-cycle thermal management systems for complete details, but essentially the APU provides the power to operate all of the 727’s electrical and environmental control systems (including cabin air conditioning and cooling for avionics) without requiring the aircraft to be hooked up to ground-based generators, ducting, or power units. The 727’s engines could also be spun up and started using the APU. This was a huge selling point for smaller, under-serviced airports with limited resources.

In a somewhat unusual move, Boeing didn’t build any prototype 727 aircraft, but instead tested partially constructed fuselages to the failure point, tested systems such as the landing gear to well beyond their service life, and listened to feedback from engineers, test pilot crews, and customers to tweak a working aircraft that, once it was satisfactory, went directly to the customer and into service with Eastern Air Lines starting on February 1, 1964.

Because Boeing was committed to getting the 727 right the first time, and testing was extremely intense, Key.Aero reports that the overall development costs of the 727 added up to $20 million more than expected, amounting to a total of $150 million, or $1.52 billion today. That’s a hefty chunk of change by anyone’s standards. However, Boeing was intent on building an airplane that was so good–and so reliable–that it would open up new jet airline routes, reduce operating costs, and save airlines money in the long run despite the fairly hefty buy-in. They hoped that the 727 would help cement Boeing as the primary choice for airline customers, and it certainly did that job admirably, far exceeding initial sales projections.

As the popularity of and demand for the new tri-jet grew, Boeing focused not only on selling a robust, reliable airliner that filled a vital need, but that could be provided in multiple variants according to specific customers’ desires. As such, Boeing offered custom (the Brits would say “bespoke”) versions of the aircraft for different airlines, including options as fundamental as how the cockpit switches and instrument panels were oriented or configured. This may have made corporate customers happy, but it caused at least some consternation with pilots who flew 727s for different airlines, or who had to deal with aircraft that were originally sold to one airline and were then purchased by another. Switches that flipped up for ON in one model of 727 might flip down for ON in another model of 727, for example. So pilots and engineers needed to stay on their proverbial toes to avoid confusion.

Despite these quirks, the 727 was considered wonderful to fly, not least because of its impressive speed and reliability. 727 pilots we’ve heard from report that the aircraft could cruise at .88-.90 Mach (Mach 1 is about 660 mph/1,063kph at 35,000 feet/10,668 meters) all day long, though pilots would typically cruise at between .84-.86 Mach to save fuel. The 727 was also the first jet airliner to break Mach 1 during testing, in a controlled dive from 40,000 feet, and it held that speed for 16 seconds.

Early 727 crashes caused public outcry, but were due to pilot error

The 727 is perhaps unique in commercial aviation in being the only aircraft we know of that has never had a mechanical-failure-related accident or crash. All of the 727’s hull losses have been determined after investigation to be due to pilot error (or terrorism). Nonetheless, 4 high-profile 727 accidents didn’t help the early popularity of the aircraft. Simple Flying says, “In August 1965, United Air Lines Flight 389 plunged into Lake Michigan while descending for landing at Chicago O'Hare. In November 1965, American Airlines Flight 383 crashed on final approach to Greater Cincinnati Airport (CVG), killing 62 of 66 passengers and crew. Three days later, United Air Lines Flight 227 crashed on landing at Salt Lake City International Airport (SLC), killing 43 of 91 aboard. Three months after that, All Nippon Airways Flight number 60 crashed into Tokyo Bay, killing all 133 people onboard.”

The sad part is that all of these crashes could have been avoided, had the pilots been more familiar with the new features and handling characteristics of the airplane. All of these crashes happened at night and in each case, the pilots had minimal experience flying the 727 (which is somewhat understandable, since the aircraft had only been in service for a year or two). When the 727’s extended flap position was set at 40 degrees for landing, it would slow the plane down dramatically and the “sink rate” or rate of descent would increase quickly. To counter this, more power than typical was needed when the 727’s extensive and complicated flaps were deployed. This was counter to some other aircraft designs, and the Civil Aeronautics Board’s investigation determined that pilots weren’t trained properly in the procedures to counteract these rapid sink rates during landings, particularly at night when visibility was limited. The FAA ordered airlines to update their training procedures and flight manuals. 

Additionally, like all T-tail planes, the 727 could stall if the plane reached a too-high angle of attack on takeoff. To counteract this, Boeing installed a “stick shaker” to warn the pilots of the danger so they could correct the angle before the aircraft stalled. 

Once properly trained on the type, pilots generally liked the 727 and it was favored by quite a few crewmembers of the time.

What are the advantages of a tri-jet or trijet airliner design?

One major advantage of the tri-jet design is that the wings can be located further aft on the fuselage, compared to twin-jets and quad-jets with all wing-mounted engines. This moves the center of gravity rearward, which improves fuel efficiency. In addition to the improved access to the service and cargo areas mentioned above, the more open fuselage space also allows the main cabin exit and entry doors to be more centrally located for quicker boarding and deplaning, ensuring shorter turnaround times and improving the passenger experience. We talked about the rear stairway underneath the central engine, which freed the crew from dependence upon airport boarding ramps (and also allowed the infamous robber and hijacker D.B. Cooper to parachute to his unknown fate from a 727 mid-flight).

Tri-jets are logically more efficient and generally cheaper than four-engine airliners, as the engines are the most expensive components on the plane, and running more engines consumes more fuel, all else being equal. The tri-jet configuration is ideally suited to mid-sized airliners carrying fewer passengers on shorter routes, which is exactly how the 727’s primary airline customers used it, although its longer-range capabilities have been exploited for closer international flights and cargo duty.

Compared to twin-jet designs of the time, the tri-jet has improved takeoff performance in the event of an engine failure. The 727 was able to take off from “hot and high” airports where lift is a concern, or where terrain clearance is a factor. 

Another potential advantage is that, unlike twin-engined airliners, tri-jets are not required to land immediately at the nearest suitable airport if one engine fails. Thus an operator might choose a further airport that is more suitable, with resources to perform any necessary repairs. 

Plus, they look frickin’ cool.

How much did a Boeing 727 cost originally?

The Boeing 727 had a unit cost of $4.25 million in 1963, which grew to $22 million by 1982. A 1980 Washington Post article reported the new purchase price of the 727-200 at between $14.5 and $17.5 million, depending on options and configuration. That 1963 price equates to around $43 million today, while the 1982 price had the buying power of around $70.7 million in today’s Monopoly money. 

So, we can see that over its first 20 years of production, the 727’s perceived value (along with its price in year-adjusted dollars) had almost doubled, despite some public-relations troubles due to the aforementioned early crashes.

A 1993 study put the then-current market value of a 727-200 (advanced) at $6.4 million, though obviously since this was 9 years after the end of production, that was for a used aircraft. Currently, at least as of the time of this publication, you can buy TWO 727s for a total price of $850,000. A bargain!

How many Boeing 727s were built?

Boeing produced a total of 1,832 of the iconic 727 tri-jet aircraft, including all variants. This far surpassed the original sales target of 250 aircraft, and the 727 proved so capable and popular that it remained in production for 22 years. 

During the late 1960s and through the 1970s, more 727s were built per year than any other jet airliner in history. In fact, the 727 was the most-produced jet airliner ever, until the 737 surpassed it in the early 1990s. 

The final Boeing 727 (a 727-200F variant) was delivered to FedEx in 1984.

Why did the 727 fall out of favor?

The original “narrowbody” jet airliner designs such as the Boeing 707, 727, and Douglas DC-8 had 6-abreast seating with a central aisle, in what today we call “economy class.” There wasn’t a lot of elbow room, nor space for larger carry-on luggage. These aircraft also were originally built with (by today’s standards) noisy and inefficient early turbofan engines. In the 1970s and 1980s, public demand for quieter jet airliners began to put pressure on manufacturers to develop less-noisy designs. Rather than go through the expense of retrofitting newer, quieter turbofan engines onto the 727 (which wouldn’t be practically feasible with its internal/tail-mounted central engine anyway), so-called “hush kits” were tried on several airliners. 

Smithsonian reports, “In 1997, James Raisbeck, a former Boeing engineer, offered what some called ‘the non-hush-kit hush kit’ for the Boeing 727-200. It reduces the angle of deflection of the wings’ leading edge slats, increases lift, and enables takeoff with reduced power and less noise. After September 11, 2001, many older aircraft, possible candidates for hush kits, were hustled off to retirement. Yet by the end of 2003, FedEx, the largest operator of Boeing 727s, held orders from 60 airlines for 740 Stage 3 [hush] kits it designed in-house.”

The fuel crisis of the 1970s added additional pressure for airline companies to prioritize fuel efficiency and maximize passenger capacity, particularly for short- to medium-length domestic routes. The more modern 2-engine airliners proved far more efficient for these purposes, and with the latest engines, are even capable of flying longer international routes as well.

Another nail in the 727’s coffin was its requirement of a flight engineer, or an additional cockpit crewmember for each flight. Modern airline passengers may not even be aware that a 3-person cockpit crew was a thing well into the 1990s. Nearly all modern airliners only require a 2-person cockpit crew consisting of a Captain and a co-pilot or first officer. Since the 727 was designed and built before many of the flight engineer’s primary tasks became automated, it still required this third member of the crew, and of course his/her salary. This added to the cost of operating a 727 compared to a more modern aircraft with many more automated systems. Pilot unions fought hard initially to retain the flight engineer position, but as the newer jets made the engineer obsolete, the writing was on the wall and the 727 was largely retired, though it still remains in service for some foreign-owned cargo routes and charter flights.

In the end, the Boeing 757 twin-jet was announced as the replacement for the 727, and remained in production until 2005. 

How many Boeing 727s are still flying?

Sources vary, but reports estimate between 35 and 40 727s are still in active flight status, primarily in cargo-transportation roles but with limited charter passenger flight service. Simple Flying reports “Serve Air Cargo in Congo is the largest operator with four active 727s, serving the domestic freight transportation market.” Nine 727s are operating in military configurations for various countries, including Burkina Faso, Congo, Colombia, Ecuador, Mexico, and Mali.

Interestingly, the first-ever 727 built flew in 2016 (53 years later), as Skytamer reports: “On March 2, 2016, the first 727 produced (N7001U), which first flew on February 9, 1963, made its final flight. The 727-100 had carried about 3 million passengers during its years of service . . . it was later sold to United Airlines, which donated it to the museum in 1991. The Federal Aviation Administration granted the museum a special permit for the 15 minute flight. The jet was restored over 25 years by the Museum of Flight in Seattle and was ferried from Paine Field in Everett, Washington to Boeing Field in Seattle, where it was put on permanent display at the Aviation Pavilion.”

The 727 remained in main line service with most major airlines until September 2001, which is an incredible 35-plus-year service history.

In the post-postmodern world where every airliner tends to resemble all the others, it’s hard not to miss the sexy-funky looks and jet-set noise of the venerable 727. Here’s hoping Boeing can figure out how to keep all of its new airplanes as boringly reliable as the 727 was.

–By Jeff Davis, Intergalactic Scribe

Sources:

https://www.youtube.com/watch?v=T7GUf9wDs9U&ab_channel=Greg%27sAirplanesandAutomobiles

https://www.skytamer.com/Boeing_727-100.html

https://simpleflying.com/boeing-727-why/

https://simpleflying.com/boeing-727-rise-fall-story/

https://simpleflying.com/boeing-727-operators-2023/

https://en.wikipedia.org/wiki/Trijet

https://simpleflying.com/boeing-727-early-struggles-excessive-descent-speeds-sink-rates/

https://www.key.aero/article/developing-boeing-727

https://en.wikipedia.org/wiki/Boeing_727