I had a call from Rob Leach a little while ago - he is leaving Oakland for Honolulu at first light (Sunday morning). Monterey was unsuitable due to fog. Winds on the route are +14 knots at present (i.e. 14 knot tailwinds overall).
Hello Clyde,
I observed Rob depart Oakland at about 1235z. Cleared the Bay Bridge above 2,000’ (a mighty feat considering how heavy the aircraft is). Flew out over the Golden Gate Bridge and then bee-lined it for PHNL.
At 1745z, he was at 135°56"W 32°25"N. Ground speed at 6,000’ was 163kts. Estimating HNL in 502 minutes or 0207z.
Hope this helps (g).
Rick.
Rob arrived in Honolulu not long ago. The trip time was just over 14 hours. Highest groundspeed seen was 170 knots.
The engine ran fine. Oil consumption was minimal. There was a failure, however. One alternator failed 3 hours into the trip. The other one continued to function quite happily. The cause will be investigated tomorrow, along with an oil change and a compression test.
The next leg is Honolulu to Christmas Island. It’s a somewhat shorter leg.
GO, Rob, GO! God speed.
Clyde, your plane is on the way, wait …
May the wind be at your back! Good Luck…ED
Rob arrived in Honolulu not long ago. The trip time was just over 14 hours. Highest groundspeed seen was 170 knots.
The engine ran fine. Oil consumption was minimal. There was a failure, however. One alternator failed 3 hours into the trip. The other one continued to function quite happily. The cause will be investigated tomorrow, along with an oil change and a compression test.
The next leg is Honolulu to Christmas Island. It’s a somewhat shorter leg.
Awesome redunduncy on the alternators.
There was a failure, however. One alternator failed 3 hours into the trip. The other one continued to function quite happily.
Out of curiosity, Clyde, I assume the failure was in the primary alternator. Is the secondary one able to carry all loads in the Cirrus, or is it just attached to some sort of emergency bus for a radio and transponder as an example?
When Rob and I flew it out to California we didn’t get a chance to read about all the systems.
Out of curiosity, Clyde, I assume the failure was in the primary alternator. Is the secondary one able to carry all loads in the Cirrus, or is it just attached to some sort of emergency bus for a radio and transponder as an example?
The failure was actually the secondary alternator (located at the rear of the engine). The alternators are similar, however the front one (ALT1) is run at a higher RPM than the rear, and is rated at 75A max while the rear (ALT2) is rated at 40A (this is at 28V, remember, so that’s quite a lot of power).
Under normal operation, the load is split about 60/40. If one fails, the other assumes the entire load, and can run all electrical equipment. There is no need to load-shed if an alternator fails.
Interestingly, in the C model, with the electric HSI, both alternators are required for IFR, while in the B model, which has a vacuum HSI, only one alternator is required. This is because of the requirement for two independent sources of power for the gyro instruments. Evidently the battery doesn’t count.
So in theory, Rob could depart Honolulu with only one alternator operating.
Interestingly, in the C model, with the electric HSI, both alternators are required for IFR, while in the B model, which has a vacuum HSI, only one alternator is required. This is because of the requirement for two independent sources of power for the gyro instruments. Evidently the battery doesn’t count.
So in theory, Rob could depart Honolulu with only one alternator operating.
Clyde, do you know if either alternator will carry the full load in the C model also? In other words, is the requirement for both for IFR in the C just regulatory or is it also an operational requirement?
Under normal operation, the load is split about 60/40. If one fails, the other assumes the entire load, and can run all electrical equipment. There is no need to load-shed if an alternator fails.
Had not been aware both alternators were on line simultaneously. At least that is a sure way to know both are operational.
I recall that when we turned on the battery switch prior to engine start that sometimes the electric vacuum pump would come on and sometimes it would not. (Forgot to write that up as a squawk – sorry!). I assume that the vacuum system does not operate like the alternators with both pumps up and running simultaneously. Does the backup pump come on automatically or does it have to be turned on manually with a switch? Or will either method work?
Also, any word from Rob yet on the cause of the alternator failure?
Interestingly, in the C model, with the electric HSI, both alternators are required for IFR, while in the B model, which has a vacuum HSI, only one alternator is required. This is because of the requirement for two independent sources of power for the gyro instruments. Evidently the battery doesn’t count.
I assume that HSI still works but that in the USA it is not legal to fly IFR without the backup.
Correct?
Clyde, do you know if either alternator will carry the full load in the C model also? In other words, is the requirement for both for IFR in the C just regulatory or is it also an operational requirement?
It’s just a regulatory requirement, since the HSI is electric in the C model. The dual alternator option on the B model is the same as the C model. Also, only one alternator is required for VFR. This is based on a table provided in the POH supplement for the dual alternator option.
Does the backup pump come on automatically or does it have to be turned on manually with a switch?
It’s automatic. It should come on when you first turn the battery on, I believe. In flight, if you lose the vacuum pump, the only thing you will see is the “vacuum fail” annunciator illuminate. Ask Walt Conley, he’s had it happen twice, I believe.
Also, any word from Rob yet on the cause of the alternator failure?
No, not yet.
I assume that HSI still works but that in the USA it is not legal to fly IFR without the backup.
Correct?
Well, I think it’s more complicated than that. The POH supplement has a table showing how many alternators you need for IFR and VFR flight, and with an electric HSI, it shows that IFR flight requires 2, and VFR requires 1.
Howevever, FAR 23.1331 requires two independent sources of power for any instrument which requires a power supply. This is not contingent on IFR or VFR, it’s just a certification requirement. So, this would mean that if one alternator on a C model failed, you would have to placard the HSI as inoperative or remove it (since it no longer meets certification). This would make the plane unairworthy for IFR, but not VFR, since you don’t have to have a DG for VFR.
Maybe I have misread the POH (I don’t have it in front of me). I will check. Maybe someone who has more knowledge of airworthiness requirements can comment.
I assume that HSI still works but that in the USA it is not legal to fly IFR without the backup.
Correct?
Well, I think it’s more complicated than that. The POH supplement has a table showing how many alternators you need for IFR and VFR flight, and with an electric HSI, it shows that IFR flight requires 2, and VFR requires 1.
Howevever, FAR 23.1331 requires two independent sources of power for any instrument which requires a power supply. This is not contingent on IFR or VFR, it’s just a certification requirement. So, this would mean that if one alternator on a C model failed, you would have to placard the HSI as inoperative or remove it (since it no longer meets certification). This would make the plane unairworthy for IFR, but not VFR, since you don’t have to have a DG for VFR.
Maybe I have misread the POH (I don’t have it in front of me). I will check. Maybe someone who has more knowledge of airworthiness requirements can comment.
I assume that HSI still works but that in the USA it is not legal to fly IFR without the backup.
Correct?
Well, I think it’s more complicated than that. The POH supplement has a table showing how many alternators you need for IFR and VFR flight, and with an electric HSI, it shows that IFR flight requires 2, and VFR requires 1.
Howevever, FAR 23.1331 requires two independent sources of power for any instrument which requires a power supply. This is not contingent on IFR or VFR, it’s just a certification requirement. So, this would mean that if one alternator on a C model failed, you would have to placard the HSI as inoperative or remove it (since it no longer meets certification). This would make the plane unairworthy for IFR, but not VFR, since you don’t have to have a DG for VFR.
Maybe I have misread the POH (I don’t have it in front of me). I will check. Maybe someone who has more knowledge of airworthiness requirements can comment.
That answer does not quite add up either. The turn and bank indicator has an electric source and is required for IFR. Every IFR aaircraft I have ever flown does not have dual alternatore to back up that instrument. For non commercial IFR flying in the US we operate under part 91 rules, not part 23. It is the operating rules, not the certification rules, that determine whether one can fly IFR or not legally.
Brian
That answer does not quite add up either. The turn and bank indicator has an electric source and is required for IFR. Every IFR aaircraft I have ever flown does not have dual alternatore to back up that instrument. For non commercial IFR flying in the US we operate under part 91 rules, not part 23. It is the operating rules, not the certification rules, that determine whether one can fly IFR or not legally.
Brian
Brian,
As I understand it the turn & bank has a completely independent power source (a couple flashlight batteries or something like that!) separate from either of the alternators or anything else on the ship’s electical system.
So I believe that with a single alternator the turn and bank does in fact have two independent power sources.
On the other hand the HSI would not have two independent sources with only one alternator.
I know between nil and zilch about certification rules but if what Clyde says is true then this could explain why the HSI would have to be placarded with only one alternator, whereas the turn & bank doesn’t.
also explains I guess why Cirrus puts a vacuum HSI in package “B” and an electric one in “C” since “C” comes with dual alternators.
Out of curiosity, does anyone know if the certification requirements are similar for vacuum driven instruments – does one need dual vacuum systems in order to use any vacuum instruments in aircraft certified under part 23?
steve
That answer does not quite add up either. The turn and bank indicator has an electric source and is required for IFR. Every IFR aaircraft I have ever flown does not have dual alternatore to back up that instrument. For non commercial IFR flying in the US we operate under part 91 rules, not part 23. It is the operating rules, not the certification rules, that determine whether one can fly IFR or not legally.
Brian
Brian,
As I understand it the turn & bank has a completely independent power source (a couple flashlight batteries or something like that!) separate from either of the alternators or anything else on the ship’s electical system.
So I believe that with a single alternator the turn and bank does in fact have two independent power sources.
On the other hand the HSI would not have two independent sources with only one alternator.
I know between nil and zilch about certification rules but if what Clyde says is true then this could explain why the HSI would have to be placarded with only one alternator, whereas the turn & bank doesn’t.
also explains I guess why Cirrus puts a vacuum HSI in package “B” and an electric one in “C” since “C” comes with dual alternators.
Out of curiosity, does anyone know if the certification requirements are similar for vacuum driven instruments – does one need dual vacuum systems in order to use any vacuum instruments in aircraft certified under part 23?
steve
Yes, the vacuum instruments require backup power as well. This is why the (relatively expensive) electric vacuum pump is standard equipment.
I don’t have my FARs handy, but I believe that the part 23 certification requirements become part 91 airworthiness issues because part 23 puts the “all power supplies must be running for IFR” requirement into the POH, and part 91 gives the POH the same regulatory power as placards in the aircraft (and supercedes the minimum equipment requirements otherwise spelled out in part 91).
Out of curiosity, does anyone know if the certification requirements are similar for vacuum driven instruments – does one need dual vacuum systems in order to use any vacuum instruments in aircraft certified under part 23?
steve
Just looked it up in Part 23. It is quite clear in FAR 23.1331a that the requirement for dual power supplies exists for both electrically and vacuum powered instruments. However, this is only a certification requirement. We don’t fly under part 23, but only design and build under it.
Since I also do not have access to a POH, I am wondering if there is something in it that supercedes the flight rules under which one is operating. For instance, flying IFR under part 91 does not require dual power sources for anything but does require that certain instruments be installed and operating. Under part 91, it seems as though the aircraft could be flown IFR or VFR if the requirments of part 91 are met. BUT, if the POH elevates the dual power supply requirment of certification to that of operation, then I suspect it rules.
I looked up the Type Certificate Data Sheet for the SR20 but it only defers to Part 23. It makes no mention of an approved Minimum Equipment List (MEL).
In general, if you do not have an approved MEL (most small planes do not), then any inop equipment must be deactivated and placarded as inop. However, if you have all the instruments and systems needed for flight under the FAR under which you are flying (part 91 in the case of the ferry), then you are normally good to go UNLESS the POH somehow mandates something else.
Thus it would seem to me that Rob could launch IFR or VFR with only one alternator and one vacuum pump under FAR 91, all completely legally, unless the POH requires more.
FYI, 10% of the FARs are black, 10% white and the other 80% are quite gray. And you can get gray trying to figure out some of them…
Clyde, a question:
Should have asked this in my last post, but in what section of the POH does it discuss the number of alternators and vacuum pumps required for VFR and IFR? Am curious if it is in Section 2 – limitations, or is specified in some placard. Either of those make it mandatory. Or is it in something that is sort of a “CYA” section where it is strongly recommended but not mandated by the FARs. You know our legal system, so something like this could be slid in to look like regulations but not be.
If it says in there somewhere that both redundant power sources are required for IFR flight, I suppose that is binding even though the U.S. part 91 does not require this. Although you guys in Oz have your own set of rules, this is an important matter to those in the U.S. who are future Cirrus owners. Not knowing for certain what the rule is in this regard can get your license suspended or void an insurance claim.
What troubles me is that FAR 23 mandates two alternators and two vacuum pumps for certification. That is clear. One could then conclude that all Cirrus aircraft need both sources in duplicate at all times for IFR because there are both electric and vacuum instruments that are required for IFR flight under part 91. The AI in this aircraft is always vacuum, I believe, and the turn coordinator is always electric and both are mandatory. Thus the electric/vacuum HSI should not even be an issue.
So the question remains – does the POH elevate the part 91 IFR requirements to some higher level and what is it? Are both dual vacuum pumps and dual alternators required for a legal IFR departure in the U.S.?
Thanks for looking it up and letting everyone know.