I have flown the MD-11 for some 4000 hrs, until 2004. In both passenger and cargo ops.
I enjoyed flying it, but it is an airplane you have to be careful with when landing.
When designing the MD-11, McDonnell Douglas reduced the size of the horizontal stabilizer compared to its predecessor DC-10, for fuel efficiency reasons.
Obviously, this reduced pitch authority to a certain extent. To compensate, LSAS was installed which has been described before. It is basically a horizontal yaw damper with a few additional softwaremodes.
After a number of tail strikes and hard landings, they added a nose-lowering mode to it. It trims the nose down after touchdown. That helped somewhat.
My experience; especially when flaring a bit late, it can surprise you by further pitching up after touchdown. Requiring a good push on the yoke to avoid a tail strike.
During the first few years that my company operated the MD-11, I have seen, and also made
, nearly full nose down inputs on the yoke, to the stops. I had never seen that on any other airplane before, nor have I seen it since.
Since then, we, the pilots, have learned to deal with this airplane’s peculiarities, and my company has not had any tail strikes or landing accidents. And hopefully it stays that way, as we still operate it. I’m sure luck has played a part in that record.
LH, FX, DL & others that have had MD-11 accidents are professional airlines with carefully selected pilots, and I’m sure they train them properly. So if these airlines have significantly more incidents and accidents with this airplane type and not with others, it must be the airplane that is different. I don’t think there is much doubt about this. The accident statistics speak for themselves.
The smaller horizontal stab gives you somewhat less control, especially at lower speeds with full flaps.
On top of that, I believe the airplane has more longitudinal inertia, due to the tail engine. That heavy engine takes time to start moving up or down.
I also wonder if the gyroscopic effects of that tail engine play a roll in this inertia.
Regardless, it requires more force to make it pitch up or down. Combined with the smaller horizontal stab, it makes pitch changes take longer than you are used to.
Let’s look at the landing.
Assume you flare a bit on the late side. Realizing this, you pull up a bit more than usual. However, due to the longitudinal inertia and smaller stab, this takes longer than you are used to. So you wonder if something is ever going to happen, and pull a bit more. Finally, the airplane begins to react; it will start to pitch up. The mains touch down. But the pitch rate will continue after touchdown due to the longitudinal inertia, added by the pitch up tendency caused by the spoilers. So a good push is needed to avoid a tail strike. Lowering the nose again takes time, perhaps causing more pitch down input than needed. When you finally get a downward pitch rate, you have to stop it again before putting the nose gear through the runway.
This is a perfect recipe up for a PIO, Pilot Induced Oscillation, which is what we have seen on several MD-11 accidents.
Anyone who has flown the MD-11 will recognize it.
This PIO is even more dangerous if you have bounced, and become airborne after the first touchdown. A go around is the only safe recovery out of this situation.
But what if you don’t realize that you bounced? Apparently, that is not as easy as it sounds, because several crews didn’t recognize being airborne again.
I don’t pretend to have an easy solution for this tricky airplane characteristic.
I don’t see a technical solution, because you cannot do anything about that horizontal stab and the tail engine. We are talking about a twenty odd year old airplane here. For Boeing it is a ‘heritance’ model, and I’m sure they would love to get rid of supporting it. They do so hesitantly now. With it's high accident rate, they probable see it as a liability.
Installing HUD's then, as proposed by the Saudi Accident board? I doubt if they would be effective. Things happen quickly during landing, instinctive reflexes take over. Reflexes that were developed on other, more benign, airplanes.
An obvious start would be bounce recognition and recovery procedure training, as several airlines do. Not only during initial-, but also during recurrent training.
Briefing this procedure during every approach briefing would help to reinforce awareness of this tricky airplane behavior.
Experience on the airplane certainly helps, as I did not see full control inputs anymore after those early years. That means that anyone who has fewer than, say, a few years on the airplane has to stay extra vigilant. And the pilot next to him/her as well.
And don’t think twice about going around.
For the mindset, it might help to always take along enough fuel for an - extra - go around (on top of the std 30 mins final reserve). That way going around becomes a bit more carefree.
An extra expense, for sure. But accidents or incidents are more expensive.
I once read a beautiful suggestion on PPRuNe; a bottle of wine each for pilots that made a go around, no questions asked. With compliments, from the MFO. FDM will take care of everything else.
Bottom line; even though the MD-11 is an airplane with certain peculiarities, it can be flown safely by experienced and professional crews.
But be careful landing it.
