EC135
Join Date: Feb 2001
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Nick
Presumably airframe manufacturers get data on engine life expectancy from the engine manufacturers, based on empirical research including actual destructive testing, from which the acft manufacturer, along with authorities, establish lifespans based on the relevant spectrum.
Out of academic interest, about how long would an engine statistically last before it would fail at say the 2min 30sec OEI limits? Just interested to know what sort of approx % reserve you guys work to.
What about tranmissions? If there is a 5 minute take off limit of say 100% Tq, what sort of Tq would you expect the MGBX to typically actually catastrophically fail at?
Presumably airframe manufacturers get data on engine life expectancy from the engine manufacturers, based on empirical research including actual destructive testing, from which the acft manufacturer, along with authorities, establish lifespans based on the relevant spectrum.
Out of academic interest, about how long would an engine statistically last before it would fail at say the 2min 30sec OEI limits? Just interested to know what sort of approx % reserve you guys work to.
What about tranmissions? If there is a 5 minute take off limit of say 100% Tq, what sort of Tq would you expect the MGBX to typically actually catastrophically fail at?
Join Date: Apr 2003
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Head Turner, 407 and rotorspeed,
You have all shown that you really understand the concept, and all your questions are valid. The problem is that the current regulations that we work to were made before it was realistic to be able to determine the actual usage so they froze the state of the art back in the 1950's. Changing the regs is a massive effort that requires a series of civil servants to stick their necks out and advocate change is a more liberal direction - after all, today's system works, so why risk my career messing with it? Remember, the CAA/FAA/JAA don't spend 5 cents operating anything, right, so there is no advantage to changing anything.
Look for a new presentation on my web site discussing this, maybe today!
You have all shown that you really understand the concept, and all your questions are valid. The problem is that the current regulations that we work to were made before it was realistic to be able to determine the actual usage so they froze the state of the art back in the 1950's. Changing the regs is a massive effort that requires a series of civil servants to stick their necks out and advocate change is a more liberal direction - after all, today's system works, so why risk my career messing with it? Remember, the CAA/FAA/JAA don't spend 5 cents operating anything, right, so there is no advantage to changing anything.
Look for a new presentation on my web site discussing this, maybe today!
Join Date: Mar 2003
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Those having problems with the electrics (EMB)must be mechanically lacking because my question is;- Why would anyone need to start an engine without a battery fitted and connected?
I come to this conclusion from the information given above. Connecting a GPU for power to operate the electrical equipment to lessen the drain on the battery during ground training is understandable, but using a GPU for a start without a fitted battery doesn't seem logical to me.
I come to this conclusion from the information given above. Connecting a GPU for power to operate the electrical equipment to lessen the drain on the battery during ground training is understandable, but using a GPU for a start without a fitted battery doesn't seem logical to me.
Head turner:
there is a little lost in the translation between ECD and us ignorant anglofiles!
The battery being physically connected to the electrics system is taken for granted. It is installed and electrically in series with the looming!
Where the confusion came in was whether the alert letter (when it stated battery must be connected) meant the battery must be swithced ON.
I have talked to ECD personally and they say:
Physically plug the external power supply into the a/c first,
THEN switch the BMS on,
THEN switch the ext pwr on.
The battery is there to act as a buffer.
there is a little lost in the translation between ECD and us ignorant anglofiles!
The battery being physically connected to the electrics system is taken for granted. It is installed and electrically in series with the looming!
Where the confusion came in was whether the alert letter (when it stated battery must be connected) meant the battery must be swithced ON.
I have talked to ECD personally and they say:
Physically plug the external power supply into the a/c first,
THEN switch the BMS on,
THEN switch the ext pwr on.
The battery is there to act as a buffer.
Join Date: Mar 2003
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One further point on the 24v issue.
I have seen the voltage drop from 25.4v to 24v during the time it takes to complete the cockpit pre start checks, once the voltage dropped to 20 volts and the GPU was connected, then switched on for the start.
Surely the minumum voltage for starting ought to be stated both in the Limitations section and in the pre start check list prior to putting engine switch to ground idle.
And instructions for disconnecting the GPU.
Failing any instructions we run both engines up to ground idle , with the BMS on. When both engines are stabilised at GI we disconnect the GPU, by switching off the GPU then removing the plug from the a/c.
I have seen the voltage drop from 25.4v to 24v during the time it takes to complete the cockpit pre start checks, once the voltage dropped to 20 volts and the GPU was connected, then switched on for the start.
Surely the minumum voltage for starting ought to be stated both in the Limitations section and in the pre start check list prior to putting engine switch to ground idle.
And instructions for disconnecting the GPU.
Failing any instructions we run both engines up to ground idle , with the BMS on. When both engines are stabilised at GI we disconnect the GPU, by switching off the GPU then removing the plug from the a/c.
Is anybody else confused by the logic of the EC information?
My understanding of the system, suggests that when you plug in the GPU and switch the Battery Master switch on, the battery and generators are isolated from the Primary Bus Bars to prevent any flow of current between Battery and GPU. If this is the case, how does the Battery act as a 'Buffer'.
Eurocopter also recommend that the battery is disconnected when operating with an EPU for an extended period of time.
TeeS
My understanding of the system, suggests that when you plug in the GPU and switch the Battery Master switch on, the battery and generators are isolated from the Primary Bus Bars to prevent any flow of current between Battery and GPU. If this is the case, how does the Battery act as a 'Buffer'.
Eurocopter also recommend that the battery is disconnected when operating with an EPU for an extended period of time.
TeeS
Hi Droopy
The wording in the manuals suggests that it is to prevent the battery running flat since it is still supplying the Battery Master Box and the Essential Bus Bar.
TeeS
The wording in the manuals suggests that it is to prevent the battery running flat since it is still supplying the Battery Master Box and the Essential Bus Bar.
TeeS
2910 Kgs as I understand it. Due to start appearing around the middle of 2006. It will also come with a change to the "Cat A" system which will make it semi automatic......... and, apparently, it's free of charge to existing T2 owners. 
Join Date: Jul 2005
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As an aside. Change to "Cat A" was going to be automatic (allegedly!). Until some bright spark pointed out that if you are flaring a bit heavy and as your airspeed drops below the threshold the Cat A kicks in - you can watch your Nr disappear off the clock! Not a good scenario! So semi-automatic it is.
Does anybody know how to fly this thing?
Does anybody know how to fly this thing?
Despite being a committed 135 fan, I could never come to terms with the designer insisting that at two fairly intense stages of flight (just after CDP and just prior to LDP) you take one hand off the controls, look and lean across the cockpit and firmly (if you jab it, you screw the system!) press a button on the far side of the cockpit! All in the name of safety!!
Without doubt, semi-automatic is the way to go - you know you are about to carry out a Cat A/confined procedure, then arm the system! If you are reducing speed for surveillance ops etc. at altitude then don’t bother.
Bobby, I know what you are saying about the Nr/Cat A switch, when I first converted to T2 I was very worried that an overenthusiastic flare would produce an overspeed, however, with many mishandled approaches under my belt I am now ‘reasonable confident’ that the fadec is competent enough to not throw in extra fuel when I am out of control! No doubt I will be proved wrong at some point.
Cheers
TeeS
Without doubt, semi-automatic is the way to go - you know you are about to carry out a Cat A/confined procedure, then arm the system! If you are reducing speed for surveillance ops etc. at altitude then don’t bother.
Bobby, I know what you are saying about the Nr/Cat A switch, when I first converted to T2 I was very worried that an overenthusiastic flare would produce an overspeed, however, with many mishandled approaches under my belt I am now ‘reasonable confident’ that the fadec is competent enough to not throw in extra fuel when I am out of control! No doubt I will be proved wrong at some point.
Cheers
TeeS
The T2 Cat A switch seems like the familiar Eurocopter cockpit/box-office design policy - let the engineers, not the pilots, decide what goes where.
If they have the wit to put a wiper-sweep switch and an ILS go-around button where they are needed, why not do the same with the Cat A? I don't mind what they choose so long as the pilot's hands don't have to move away from their normal positions on the collective and cyclic.
Then perhaps they can start on all the other controls that need sorting... getting rid of switches in the roof would be an excellent beginning.
If they have the wit to put a wiper-sweep switch and an ILS go-around button where they are needed, why not do the same with the Cat A? I don't mind what they choose so long as the pilot's hands don't have to move away from their normal positions on the collective and cyclic.
Then perhaps they can start on all the other controls that need sorting... getting rid of switches in the roof would be an excellent beginning.
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The gripe about the 'CAT A' is a very important and flight safety gripe which I also find hard to understand the logic of putting the switch in such an awkward position. An arming button on the left side of the collective switch box would have been a better choice.
For those who remember the tragic accident in Northern Ireland a couple of years ago which more than likely happened because of a badly sited wiper on/off switch.
There are many gripes about the MD902 but in my opinion the cockpit switch logic and layout is the best I've come across.
However, the weight increase must be eagerly awaited by all users, so EADS get your finger out!
For those who remember the tragic accident in Northern Ireland a couple of years ago which more than likely happened because of a badly sited wiper on/off switch.
There are many gripes about the MD902 but in my opinion the cockpit switch logic and layout is the best I've come across.
However, the weight increase must be eagerly awaited by all users, so EADS get your finger out!
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Now, as I understand it, and I could be wrong - the cat A system is fitted only because of a noise certification issue, nothing to do with safety, its a lot of work just for 3% Nr. The 145 has an automatic Cat A and I believe works just fine.
Interesting that the upgrade will be free to T2 owners, I didn't think ECD did anything for free!
I have to agree with some of the comments about switchology on the 135, some strange ideas about where to put things.
Interesting that the upgrade will be free to T2 owners, I didn't think ECD did anything for free!
I have to agree with some of the comments about switchology on the 135, some strange ideas about where to put things.