A while ago I came across an extensive document from NASA Dryden center where they tested a MD11 capability in landing with engine thrust only to control flight path all the way down to landing. Initially they tested turning, and then climbing, descending level by having the pilot control throttles, then they tried a landing. Needless to say it didn't go to well due to the increased lag of the engines EPR. Then a simple software modification to the FCC1 enabled them to use the normal controls (yoke) to control aircraft even with full hydraulic failure. The yoke would control the actual engines instead. Despite of the delay in response, control was excellent. To top things off they modified FCC1 to accept ILS-coupled landing with PCA, with 2 stages of flare. Hands off landings were done with incredible results: 1 feet off centerline, 5 feet/minute touchdown rate, 1200 feet down on the runway. Pretty incredible with the only modification a software one. The document is much more interesting read and it is available here:http://www.nasa.gov/centers/dryden/pdf/88425main_H-2107.pdfI've seen this being discussed before but this material hasn't been published before. Enjoy!

A while ago I came across an extensive document from NASA Dryden center where they tested a MD11 capability in landing with engine thrust only to control flight path all the way down to landing. Initially they tested turning, and then climbing, descending level by having the pilot control throttles, then they tried a landing. Needless to say it didn't go to well due to the increased lag of the engines EPR. Then a simple software modification to the FCC1 enabled them to use the normal controls (yoke) to control aircraft even with full hydraulic failure. The yoke would control the actual engines instead. Despite of the delay in response, control was excellent. To top things off they modified FCC1 to accept ILS-coupled landing with PCA, with 2 stages of flare. Hands off landings were done with incredible results: 1 feet off centerline, 5 feet/minute touchdown rate, 1200 feet down on the runway. Pretty incredible with the only modification a software one. The document is much more interesting read and it is available here:http://www.nasa.gov/centers/dryden/pdf/88425main_H-2107.pdfI've seen this being discussed before but this material hasn't been published before. Enjoy!

This was the first thing that got me interested in the MD11. Thanks, great read!

My question is, if it is only a software modification, and they developed it already at least for the MD-11, why did they [NASA] decide that it didn't make sense to install it after all due to the few cases of full HYD press lost? I mean, for the MD-11 everything had already been created, so the cost to modify existing one at this point would have been minute. It's not like they needed to modify hardware inside the plane.

My question is, if it is only a software modification, and they developed it already at least for the MD-11, why did they [NASA] decide that it didn't make sense to install it after all due to the few cases of full HYD press lost? I mean, for the MD-11 everything had already been created, so the cost to modify existing one at this point would have been minute. It's not like they needed to modify hardware inside the plane.

It would still cost way too much for any airline to consider purchasing. Airlines have to be incredibly tight fisted to survive, the chance of a full HYD failure is too slim to justify installing this onto a fleet.

It would still cost way too much for any airline to consider purchasing. Airlines have to be incredibly tight fisted to survive, the chance of a full HYD failure is too slim to justify installing this onto a fleet.

What is the cost in this situation? Intellectual property cost? Being a software update only. I can only see that there is a cost associated with taking the aircraft out for servicing but they would normally do that anyway for example for Pegasus -912 to -920 FMC update at some point. All I can imagine is that the software modification made by NASA is in a very primitive alpha state and would require farther extensive development to finalize and approve it for regular operation.