One Pilot’s Perspective: 737 vs. MD80
Well I have to confess, I’ve been a little “out of touch.”
Since the early 90’s, I’ve been flying the MD80, assuming as I did that as airliners went, the jet was comparable to other commercial airliners.
What a wake-up call.
In the past twenty years, technology has marched on in all manufacturing and the airline biz is no exception. Sure, there have been several add-on systems that have helped the MD80 struggle along in today’s airline environment. But that’s pretty much the macro and micro view of the problem with the MD80: rather than redesign, MacDonnell-Douglas just added a few things to an already aging airframe.
By contrast, Boeing has kept pace with new capabilities by redesigning and refining what’s worked well. When they enlarged the 737 to the present -800 model I fly, they added more wing and more power with the newest CFM-56 engines with 27,000 pounds of thrust each. Douglas stretched the DC-9 by adding fuselage plugs before and after the same old wing. And the engines are the same Pratt & Whitney JT8Ds they hung on the first ones in 1981.
It’s the difference between “add on” and “redesign” and the results of these two philosophies couldn’t be more apparent to the hands-on pilot. So let’s start with that perspective, taking a look at each from a pilot’s standpoint.
Here’s the captain’s seat of the MD80 where my butt has been for at least 12,000 flight hours. At first glance, it doesn’t look like much but I learned to make it home: everything you need is within reasonable reach and locations and function make decent sense. There’s elbow room, plus room to stow stuff at your fingertips. That’s important.
But the downside? Outside visibility is poor. The windows are small, and where the side window meets the forward windshield there’s a huge blind spot I always worried about. That plus the fact that the forward windows were in three panes and even more visibility is blocked.
And it’s not just outside visibility that’s a problem in the MD80 cockpit. Almost worse and certainly annoying is the fact that the yoke actually blocks the pilots’ view of the navigation display. That’s an unbelieveably clumsy design and shows typical disregard for the basics of human factors engineering.
Much better viz both inside and outside the 737. The seat is as comfortable and eureka! There’s a headrest–not so on the MD80. All of the 737 displays are readily reachable and easy to handle. The drawback? Not as much stowage or elbow room. Maybe the Boeing theory is that there’s ample display of anything you’d need a chart for, so you don’t need the side table to set up books and approach charts. It’s taking some creative adaptation on my part to get things in the “nest” where they’re useful, but that’s a fair trade for all of the improvements in displays and visibility in the Boeing.
Okay, that’s a quick look inside the cockpit. But the bigger question is, how do they compare flying-wise? And not sitting in the back which is, despite the frequent flyer nose-in-the-air attitude about it, “riding,” not flying.
Well, the first thing about the MD80 you notice is that at most gross weights, it accelerates and climbs fast. It’s pretty much standard on an average day that once you get off the ground and are sure you won’t strike the tail on the runway, you’re going to climb at 20 degrees nose high.
But the 737 is even more powerful and you can feel it, particularly at the higher thrust ratings which we sometimes uses on short runways. It too accelerates well and climbs without a fuss–from 600 feet at DFW to 38,000 feet in less than twenty minutes, a pretty good rate for an airliner.
That’s because of the wing: Boeing added three feet to each wing, plus the winglet as well. Never flew the plane before it had winglets, but that seems to give it a tightness in turbulence that’s probably not real popular in back. But the wing loading as a result of the broad spar structure gives it a solid feel which reminds me of the DC10: you set the pitch and bank and it wants to hold it.
The MD80 must be wrestled down final because it shows a real vulnerability to induced roll moment. That is, a gust on one wing seems to more adversely lift that wing both higher and more extremely than you experience with the 737. Again, the wingloading on the Boeing is less, so the effects are less extreme. And at the top of the cruise envelope, you can rely on the 737 wing and engines: when you have to turn on the engine and airfoil anti-ice, there’s power and lift to spare. The MD80? Good luck.
Add to that the limitations of the MD80 ailerons: they’re not hydraulically boosted. Rather, they “fly” into position by means of a tab that is displaced by the control wheel. This induces an input lag (the tab has to be moved, then gain airload) which induces a slow response, plus I feel like the MD80 spoilers when they’re activated at slow speeds induce more unpleasant drag and sink than the 737’s again, probably, due to the high wing loading on the MD80.
The effect is even worse, too, on the MD80 because the rudder is nearly useless for anything other than slewing the nose around to extract the crosswind crab on short final. A Boeing rudder is actually as effective or even more effective (no spoiler float) than ailerons for making small (3-5 degrees) heading changes on final. The MD80, being a long tube, resists rudder input which only seems to induce an uncomfortable twisting moment. Bad combination with cumbersome ailerons an sluggish roll response.
I’m enjoying the tight, hydraulically boosted roll response on the 737. granted, after take-off and on departure, roll rates aren’t really important because there’s not much maneuvering required at anything other than standard rate. In that case, both jets have the response required and plenty of power.
But on approach, especially a visual approach, there’s no comparison: the 737 has fast response from a stable wing: it wants to stay where you put it, versus the MD80 that is squirrely all the way down final and on the runway until below about 90 knots. Used to think the MD80 had the techno edge over other airliners because of the autobrakes: when 727s were wrestling large crosswinds to land on a longer runway, we could stop just fine on a shorter, into-the-wind runway. But now, the 737 has a smoother system with 4 landing settings that is superior to the MD80’s older first generation system.
Flight guidance? I was always happy with the MD80 command bar display system. To me, especially after so many hours, the command bars (the “hojo” wings) to me seem more easily assumable than the 737 crossbars which are a throwback to the old 727 or DC10 era.
Nonetheless, the 737 primary flight display is much larger and consolidates more data: airspeed, angle of attack–which the MD80 doesn’t even have–airspeed, vertical velocity, radio altimeter, barometric altimeter and flight mode annunciation as well as active frequency and identifiers. Make crosschecking easy and efficient.
Of course, the crosscheck is almost moot from the left seat which has the Head Up Display, or “HUD,” which synthesizes all of the information on my primary flight display–plus a few extras–and projects it all onto the glass in front of me. Essentially, I look through the information as we fly. It’s an amazing asset for poor weather and low visibility departures and approaches.
Night before last, going into a squally, low viz and gusty crosswind approach in Seattle, it was invaluable. Yes, it did take self-discipline to not look down and crosscheck the primary flight display, to instead trust the symbol generator and projector to not let me down in mid approach. But it was flawless: the generated runway target was a perfect overlay of the actual runway when we broke out of the soup at about 300 feet.
Well, there’s no comparison, ultimately, for me. The 737-800 is the product of years of refinement in both engineering and application. I guess once Rip VanWinkle wakes, there’s just no return to the slumberland of yore.
For me, this is a great way to fly; in fact, the only way from now on!