Finnish-modified F-18D Hornet crashes
Join Date: Jan 2003
Location: Manchester
Posts: 323
Likes: 0
Received 0 Likes
on
0 Posts
Thank goodness "Maverick" and "Goose" got out. Nasty wounds though
My knowlage of the Hornets fly-by-wire system is nil but I have sat through lectures on the A320 and 777 systems. What strikes me as odd is that the system went straight to manual and missed out any degraded steps. Anybody know the Hornet's FBW system?
Also have they said if the engines were running after the tail slide?
Rgds Dr I
My knowlage of the Hornets fly-by-wire system is nil but I have sat through lectures on the A320 and 777 systems. What strikes me as odd is that the system went straight to manual and missed out any degraded steps. Anybody know the Hornet's FBW system?
Also have they said if the engines were running after the tail slide?
Rgds Dr I
Thread Starter
No word yet about whether the engines were producing power. Literally translated, the press release says airspeed grew critical during "recovery attempts" (plural) which might include changes in power settings, of course. Efforts to find out the reason(s) for the control system reversion are expected to take weeks.
Join Date: Apr 2009
Location: Sydney
Age: 45
Posts: 243
Likes: 0
Received 0 Likes
on
0 Posts
The Hornet FBW system consists of four computers that take the pilots comands and figure out the control surface deflections required to perform the required action. They each "vote" on the action and if one disagrees with the rest it is deemed to have failed. If all fail then the system reverts to direct electrical back up of all control surfaces. If that fails there is a cable back up to the horizontal tails only as a get home or out of danger device. Don't know if you could land the aircraft like this.
Anyone with a more detailed knowlage of the FBW system please correct me if i'm wrong!!!!
Anyone with a more detailed knowlage of the FBW system please correct me if i'm wrong!!!!
Join Date: Apr 2009
Location: Sydney
Age: 45
Posts: 243
Likes: 0
Received 0 Likes
on
0 Posts
Thanks dat581. I Googled violently and couldn't see anything. I assume that there are multiple channels within each box as well as per Airbus and Boeing?
Rgds Cking
Rgds Cking
Any RAAF, CAF or USN blokes care to enlighten us?
Thread Starter
Join Date: Jan 2003
Location: Manchester
Posts: 323
Likes: 0
Received 0 Likes
on
0 Posts
Thats an interesting webite!
So as I read it. Two computers each with two channels. So four channels BEFORE it goes to manual.
Oh for a schematic of the power sources!!!!
Rgds and thanks
Dr I
So as I read it. Two computers each with two channels. So four channels BEFORE it goes to manual.
Oh for a schematic of the power sources!!!!
Rgds and thanks
Dr I
Join Date: Apr 2009
Location: Sydney
Age: 45
Posts: 243
Likes: 0
Received 0 Likes
on
0 Posts
One gererator on each engine I don't know how many batteries plus one emergency battery which lasts about 20 minutes at best. The Super has I think nine diffferent power sources and no mechanical back up to the controls.
Thread Starter
The Air Force has published a shortish bulletin dated June 29 but in Finnish only, I´m afraid. Here are the findings so far: according to flight recorder data, either a mechanical or a hydraulic fault was discovered by the control system in the servo cylinder of the right stabilator. This finding led to the system shutting down the electrical control mechanism of both stabilators and switching over to mechanical backup (MECH-ON state). Attempts to regain electric control of the stabilators failed. All other control surfaces remained under normal control. The investigation continues.
That´s as accurate a translation as I´m able to make at this point.
That´s as accurate a translation as I´m able to make at this point.
Thread Starter
A press release has been published, confirming the above. During the tail slide, a fault occurred in the r/h stabilator servo cylinder valve which caused the stabilators to move in opposite directions. This again caused the system to revert to mech backup. There was not enough time nor ability to regain control using the mech backup system only so the command was given to eject. Full report only available for interim use by the Air Force and the press release can not be linked to, so you´ll have to take my word for it, I guess.
Join Date: Apr 2010
Location: Scandinavia
Age: 59
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
"confirm" - "afirm"
I can vouch that FINN47 has translated the Finnish text correctly.
I was actually working down the hall from the guy´s office who was in charge of the accident board for a few months last year - the other pilot was my classmate in the academy - and the other guy was a student on a course that I was in charge of in -05/06.
BTW, the plane hit the ground (hard), just a few clicks away from the church where I was married - longlongtimeago - a sign perhaps
I was actually working down the hall from the guy´s office who was in charge of the accident board for a few months last year - the other pilot was my classmate in the academy - and the other guy was a student on a course that I was in charge of in -05/06.
BTW, the plane hit the ground (hard), just a few clicks away from the church where I was married - longlongtimeago - a sign perhaps
Thread Starter
Summary of events is available in English, here is the crucial part copied from the Air Force website:
As soon as the accident aircraft had entered a vertical dive the primary valve in the servocylinder that operates the right-hand stabilator failed; this resulted in differential stabilator deflection, and the flight control system reverted to the backup mechanical mode.
In normal operation inputs from the cockpit mounted flight controls are transmitted to the control surface servocylinders electrically. These inputs are processed by a flight control computer that commands the servocylinders for control surface deflection required for desired aircraft motion.
The backup mechanical mode uses cables and linkages to transmit control stick deflections to the two stabilator servocylinders for continued, albeit significantly degraded, stabilator control authority.
The other flight control surfaces remained under electrical control throughout the accident flight.
Attempts to Restore Normal Flight Control System Operation Failed
The reversion of the flight control system to the mechanical mode caused prolonged tailslide induced oscillations. Recovery from dive cannot be initiated until these oscillations have subsided; once this was achieved, the pilots initiated recovery and attempted to restore the electrical control of the stabilators, but this was precluded by the failure in the servocylinder.
During the recovery attempt, the aircraft failed to respond normally to the application of aft stick while speed was approaching the critical ejection speed. The crew ejected at approximately 875 km/h at the altitude of approximately five kilometers. The aircraft impacted terrain at 1147 hours and was completely destroyed.
The pilots sustained permanent injuries in the high-speed ejection. They are currently on convalescent leave and undergoing a medical rehabilitation program.
In normal operation inputs from the cockpit mounted flight controls are transmitted to the control surface servocylinders electrically. These inputs are processed by a flight control computer that commands the servocylinders for control surface deflection required for desired aircraft motion.
The backup mechanical mode uses cables and linkages to transmit control stick deflections to the two stabilator servocylinders for continued, albeit significantly degraded, stabilator control authority.
The other flight control surfaces remained under electrical control throughout the accident flight.
Attempts to Restore Normal Flight Control System Operation Failed
The reversion of the flight control system to the mechanical mode caused prolonged tailslide induced oscillations. Recovery from dive cannot be initiated until these oscillations have subsided; once this was achieved, the pilots initiated recovery and attempted to restore the electrical control of the stabilators, but this was precluded by the failure in the servocylinder.
During the recovery attempt, the aircraft failed to respond normally to the application of aft stick while speed was approaching the critical ejection speed. The crew ejected at approximately 875 km/h at the altitude of approximately five kilometers. The aircraft impacted terrain at 1147 hours and was completely destroyed.
The pilots sustained permanent injuries in the high-speed ejection. They are currently on convalescent leave and undergoing a medical rehabilitation program.
