Originally Posted by
Freds Ex
number 4.
Like I said, that metric is a good starting point to a safety assessment, but you're stopping at the starting point instead of asking a lot of essential follow-up questions such as
"why is the hull loss rate high?"
"what has been done to mitigate the issues since the majority of those hull losses?"
"was this most recent issue preventable with better maintenance inspections or procedures?"
"will those inspections and procedures be improved?"
and so on.
I partially agree with you. We should ask why the hull loss rate is high, and what can be or has been done to mitigate it. If, for example, the MD-11 was consistently being flown into a combat zone or to a dirt runway at 10000 feet above sea level then perhaps it would make sense to look at those as possible reasons why the hull loss rate is so much higher. But its not. Its has been flown to the same airports with the same cadre of pilots in the same or similar conditions as all of the other aircraft. So why IS the hull loss rate so much higher. I invite your answer, but in the meantime I propose at least two possibilities:
1) The redesign from DC-10 to MD-11...adding weight and length without substantially redesigning the wing and tail. As far as I can find this has resulted in higher speeds on landing, less stability (hence the LSAS), higher wing loading. Combine all of these items and you have an aircraft that is very unforgiving the landing enviroment. At this point in the life of the aircraft I very much doubt that we will see a complete redesign to address all of these deficiencies. Thus the only possible (partial) mitigation is enhanced crew training.
2) The design of the landing gear and wing attachment. In several of the MD hull loss accidents which occurred in the landing environment (after a hard or bounced landing) one wing detached from the aircraft while the other wing continued to provide lift. In the instances where this occurred the reuslt is almost always that the aircraft rolls over. The design failure mode and strength of the gear and wing roots is a significant design decision that cannot be changed after the fact without significant expense, which is probably not economical.
Here is the extract from the JTSB report on FDX80. You can find a similar discussion in the NTSB report for Newark.
"It is somewhat likely that, if the fuse pin in the MLG support structure had failed and the MLG had been separated in the overload condition in which the vertical load is the primary component, the damage to the fuel tanks would have been reduced to prevent the fire from developing rapidly. It is probable that the fuse pin did not fail because the failure mode was not assumed under an overload condition in which the vertical load is the primary component due to the interpretation of the requirement at the time of type certification for the MD-11 series airplanes."
Originally Posted by
Freds Ex
It boils down to thinking one or two ways:
1. "what is the risk of being on an MD-11, and has it been effectively mitigated?"
or
2. "this bad thing happened on the MD-11 which means the airplane is never going to be safe again even if they adequately mitigate the risk"
Decisions and opinions made using only one highlighted statistic without giving weight to much else are not well thought out. Emotional response vs rational thought.
The risk is multiple things as highlighted above, only some of which can/will be mitigated due to the age of the aircraft and probably limited remaining lifespan. Yes a bad thing happened on the airplane. Does that mean it will never be safe? Of course not...with enough time, money, and effort I suspect the airplane could be made as safe as any other. I'm repeating myself, but I don't think the economic justification is there to make these kinds of changes.
Originally Posted by
Freds Ex
Let's say Boeing builds a new airplane, certifies it, and sells it. It flies for a year without a hull loss. Does that make it a safer airplane? If you measure it by hull loss per departure, sure, but that doesn't actually mean it's a safer airplane.
Yes, but that's not what we're talking about here. All of the aircraft under consideration have a history of millions of departures.
Originally Posted by
Freds Ex
The 737 MAX had the lowest hull loss rate per departure up until the moment it didn't. Has Boeing adequately mitigated the risk since? Will you still get on a 737 MAX?
The 787 has one hull loss due to what is almost certainly a pilot decision, how is that weighted? does that airplane become less safe than it was the day before it happened?
Again, these statistical anomalies are washed out over millions of departures. Latest information I could find on 787 number of departures is ~5 million (from Boeing in April 2025), so the hull loss rate including the June 2025 accident is at most 1/5,000,000 = 0.2 per million departures, vs ~3.125 per million departures for the MD. Presently the hull loss rate per million departures for the 737 MAX is 0.41...again, (approximately) an order of magnitude better than the MD.
I've said just about all I have to say on the topic, so I'll give you guys and gals the last word. As I told Adler earlier I don't make the decisions on what types FDX or UPS decide to fly. I can only speak for myself. If you think my decision is an emotional one so be it. I've tried to lay out my argument clearly, with statistics that (as far as I can tell) are widely accepted in the aviation safety world as relevant and informative.