Unsheduled Maintence
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Unsheduled Maintenance
Curious me has a question....
How many hours can a helicopter fly until a 'grease monkey' has to check it out? Now, i'm not talking about annual, 100hr or sheduled maintenance.
I was wondering because I read somewhere that you need to keep a mechanic around (employ one) if you plan on flying a helicopter in rural areas away from maintenance facilities.
So I went looking at various helicopters' product specs. The bell206 has 0.354 MH/FH for unsheduled maintenance - does that mean i can fly close to 3 hours before a mechanic has to look it over? The R44 has something like 0.1 MH/FH - Can i conclude from this that the robinson can fly a lot longer before a maintenance guy has to take a look?
In an airplane, i can potentially fly 100 hours, assuming nothing breaks, before a maintenance guy has to check it out. Does the same hold true for Helicopters, or are their certain intervals where maintenance guys have to do some work?
Now i'm not talking about preventative maintenance, like adding oil, the pilot can do - i'm talking about work only an authorized A&P (or equivilent certification) can perform.
The question arises, because how would that work if I leased a helicopter from a major airport, flew it around the country for 15 hours before I brought it back - would maintenance guys at other airports have to look at it?
As you can see, I am a little confused
How many hours can a helicopter fly until a 'grease monkey' has to check it out? Now, i'm not talking about annual, 100hr or sheduled maintenance.
I was wondering because I read somewhere that you need to keep a mechanic around (employ one) if you plan on flying a helicopter in rural areas away from maintenance facilities.
So I went looking at various helicopters' product specs. The bell206 has 0.354 MH/FH for unsheduled maintenance - does that mean i can fly close to 3 hours before a mechanic has to look it over? The R44 has something like 0.1 MH/FH - Can i conclude from this that the robinson can fly a lot longer before a maintenance guy has to take a look?
In an airplane, i can potentially fly 100 hours, assuming nothing breaks, before a maintenance guy has to check it out. Does the same hold true for Helicopters, or are their certain intervals where maintenance guys have to do some work?
Now i'm not talking about preventative maintenance, like adding oil, the pilot can do - i'm talking about work only an authorized A&P (or equivilent certification) can perform.
The question arises, because how would that work if I leased a helicopter from a major airport, flew it around the country for 15 hours before I brought it back - would maintenance guys at other airports have to look at it?
As you can see, I am a little confused
Last edited by mattpilot; 25th Oct 2004 at 03:30.
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The R44 has 50 hr oil changes and 100 hr checks. In between those, it gets looked at by eagle-eyed pilots in a daily Check A.
I've never heard of the requirement to have a mechanic around if you are "rural" - but there again I'm not under FAA rules.
I've never heard of the requirement to have a mechanic around if you are "rural" - but there again I'm not under FAA rules.
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mattpilot,
It depends which maintenance schedule your aircraft comes under. These can vary, subject to CAA / FAA approval, for a particular aircraft, but you can't hop from one schedule to another.
You cannot normally overfly a check, so that you DO need to make sure your aircraft is is in the right place to be seen by an engineer with the required qualifications. This can be a big logistical problem at times and certainly needs to be taken into consideration if planning a long trip away from base. Certain checks CAN be brought forward, so that you can get some hours "in the bank" if you expect to be away for some time. We have to consider this on a daily basis, as we fly a lot of hours and don't always rtb at night.
As I'm not an engineer, and most of us here aren't, I suggest you post this question on the engineer's thread. Your maintenance organisation is the authority, of course.
It depends which maintenance schedule your aircraft comes under. These can vary, subject to CAA / FAA approval, for a particular aircraft, but you can't hop from one schedule to another.
You cannot normally overfly a check, so that you DO need to make sure your aircraft is is in the right place to be seen by an engineer with the required qualifications. This can be a big logistical problem at times and certainly needs to be taken into consideration if planning a long trip away from base. Certain checks CAN be brought forward, so that you can get some hours "in the bank" if you expect to be away for some time. We have to consider this on a daily basis, as we fly a lot of hours and don't always rtb at night.
As I'm not an engineer, and most of us here aren't, I suggest you post this question on the engineer's thread. Your maintenance organisation is the authority, of course.
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thanks for the replies!
I understand the aircraft would have to be checked out at certain intervals, and i'd put that under sheduled maintenance.
But i'm wondering about unsheduled maintenance & on-condition inspections.
Can i hold the same true for a helicopter as i do for a airplane, when i say i can fly the helicopter from one sheduled maintenance interval to the next, assuming nothing critical breaks inbetween, without having to have a mechanic check it out?
I am just confused by the statement that i read, that one should (not a regulation) employ a maintenance guy to periodically check out the aircraft every few hours. This would also be the reason why people with both a pilots license and A&P license are preferred by corporate employers.
So assuming Part 91 operations, how many hours can a helicopter (any, ex. if you'd like) log before it needs to get checked out - based on your own experience?
Thanks again!
**edit: I'm also asking because i'd like to know what a good 'private'/corporate helicopter is where one can fly for longer periods of time before it needs maintenance. The Bell407 has something like .751 MH/FH for unscheduled maintenance listed. To me, this indicates it needs lots of maintenance work... true?
I understand the aircraft would have to be checked out at certain intervals, and i'd put that under sheduled maintenance.
But i'm wondering about unsheduled maintenance & on-condition inspections.
Can i hold the same true for a helicopter as i do for a airplane, when i say i can fly the helicopter from one sheduled maintenance interval to the next, assuming nothing critical breaks inbetween, without having to have a mechanic check it out?
I am just confused by the statement that i read, that one should (not a regulation) employ a maintenance guy to periodically check out the aircraft every few hours. This would also be the reason why people with both a pilots license and A&P license are preferred by corporate employers.
So assuming Part 91 operations, how many hours can a helicopter (any, ex. if you'd like) log before it needs to get checked out - based on your own experience?
Thanks again!
**edit: I'm also asking because i'd like to know what a good 'private'/corporate helicopter is where one can fly for longer periods of time before it needs maintenance. The Bell407 has something like .751 MH/FH for unscheduled maintenance listed. To me, this indicates it needs lots of maintenance work... true?
Last edited by mattpilot; 25th Oct 2004 at 03:32.
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Abra cadabra..Poof, I got a number.
To: mattpilot
It is a very difficult question to answer because you have to consider the "predicted failure rates" that would require maintenance but not effect the mission of the aircraft as well as the "predicted failure rates" that would effect the mission of the aircraft.
The MMH/FH unscheduled maintenance is based on a statistical average for the collective failure rates for the aircraft. The fact that a figure is given for unscheduled maintenance per flight hour does not mean that something will fail requiring some sort of repair or correcrtive action.
The Bell figure of 0.354 MH/FH is a result of the statistical average. If that aircraft has good maintenance and all parts are changed according to spec then you might experience .035 MMH/FH unscheduled. Conversely if the helicopter is subject to hard use and not properly maintained you might experience 3.54 MMH/FH unscheduled.
Here are some figures for an attack helicopter that I worked on. Even though these were the numbers given to the customer they never reached the stated numbers because of faulty predictions.
MTBF Logistic MTBF Mission
Aircraft level 3.5 30.0
Flight control 90.9 522.6
Transmission 30.7 328.0
Structures 46.0 2069.0
Defensive Sys. 208.0 2008.0
The logistic failure rate is like the unscheduled maintenance in your question. However some of the elements in those systems make take ten to fifteen Maintenance Man Hours to repair so the figures quoted for MMH/Logistic (Unscheduled) are an average of all of the repairs for that system and these figures are averaged out for the entire aircraft.
So don't believe the figures quoted by Bell, Robinson or any other aircraft manufacturer.
Note: There should be several spaces between MTBF Logistic and MTBF Mission.
It is a very difficult question to answer because you have to consider the "predicted failure rates" that would require maintenance but not effect the mission of the aircraft as well as the "predicted failure rates" that would effect the mission of the aircraft.
The MMH/FH unscheduled maintenance is based on a statistical average for the collective failure rates for the aircraft. The fact that a figure is given for unscheduled maintenance per flight hour does not mean that something will fail requiring some sort of repair or correcrtive action.
The Bell figure of 0.354 MH/FH is a result of the statistical average. If that aircraft has good maintenance and all parts are changed according to spec then you might experience .035 MMH/FH unscheduled. Conversely if the helicopter is subject to hard use and not properly maintained you might experience 3.54 MMH/FH unscheduled.
Here are some figures for an attack helicopter that I worked on. Even though these were the numbers given to the customer they never reached the stated numbers because of faulty predictions.
MTBF Logistic MTBF Mission
Aircraft level 3.5 30.0
Flight control 90.9 522.6
Transmission 30.7 328.0
Structures 46.0 2069.0
Defensive Sys. 208.0 2008.0
The logistic failure rate is like the unscheduled maintenance in your question. However some of the elements in those systems make take ten to fifteen Maintenance Man Hours to repair so the figures quoted for MMH/Logistic (Unscheduled) are an average of all of the repairs for that system and these figures are averaged out for the entire aircraft.
So don't believe the figures quoted by Bell, Robinson or any other aircraft manufacturer.
Note: There should be several spaces between MTBF Logistic and MTBF Mission.
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Under part 91 you can fly it between required maintence without having it checked just like fixed wings.
The helicopter I fly (A-Star) lives 35 minutes from its home base and unless something needs to be fixed by a certified mechanic, it only sees a mechanic every hundred hours or if a time related item is due. The logistics of this can be huge as if one finds an problem, the mechanics will have to go to that location, and do an onsite repair which can involve cranes and such.
Between my partner and I, we put about 1,400 hours on the helicopter we have up here. It goes through 100 hour checks and as far as any unscheduled checks, we end up having to fly the helicopters to the mechanics for minor stuff about once every other month, and have a mechanic fly up due to airworthy concern about one or two times a year. Heck, we have more unsheduled maintence problems on radio equipment then mechanical.
Remember that this is for a "small" helicopter. The bigger one gets the more maintence and you start into daily required inspections that only a certified mechanic can do.
The helicopter I fly (A-Star) lives 35 minutes from its home base and unless something needs to be fixed by a certified mechanic, it only sees a mechanic every hundred hours or if a time related item is due. The logistics of this can be huge as if one finds an problem, the mechanics will have to go to that location, and do an onsite repair which can involve cranes and such.
Between my partner and I, we put about 1,400 hours on the helicopter we have up here. It goes through 100 hour checks and as far as any unscheduled checks, we end up having to fly the helicopters to the mechanics for minor stuff about once every other month, and have a mechanic fly up due to airworthy concern about one or two times a year. Heck, we have more unsheduled maintence problems on radio equipment then mechanical.
Remember that this is for a "small" helicopter. The bigger one gets the more maintence and you start into daily required inspections that only a certified mechanic can do.
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Our elderly R44 has flown 300hrs this year. 25hr oil changes done by me (pilot not engineer), 50, 100 and annual done as scheduled albeit with 10% extensions signed off by engineer. In this time we had one failure that required an unscheduled trip to maintenance (aircaft off line for 3 weeks) and a couple of snags that were dealt with at the next sheduled maintenance.
Hope that helps.
Hope that helps.
