Peter wrote:
Assuming the drive belt is intact (if not, propeller has to come off to change it)
That’s the reason why I have a spare belt wrapped around the front part of the engine. If the belt fails, I have one more shot before the propeller needs to come off…
In a single with electronic ignition I think the risk assessment would be different. At my airfield a C172 and a PA28 have recently had one magneto replaced with electronic ignition. There is no battery backup in the system, so a loss of ship’s power kills the electronic ignition immediately, hanging the engine on the single magneto. With the prospect of likely alternator failure, possible loss of electrical power, and a remote but existing risk of failure of the single magneto – without power to squawk or make emergency calls (or run the flaps if electric) – then I would probably regard it as a no-go except perhaps for short hops if taking off with a fully charged battery.
Similar considerations would apply for e.g. Thielert diesels with FADEC, where the engine is 100% dependant on electric power but there is a dedicated backup battery for the ECU’s.
The belt had come off and was damaged (not completely broken) when I landed at a fairly isolated island strip (2018). I removed the engine hood, cut the belt off completely and checked for visible damage. I called a fellow pilot who is also a mechanic and discussed the situation, and I concluded it was safe to go (without an alternator belt). The battery could run the avionics but not start the engine. After checking weather and NOTAMs once more, I hand propped and flew back home. My home field is controlled with ATC and I had planned with landing at nearby strip in case I ran out of battery for the VHF. However, when I explained my situation to my ATC 40 NM out, they gave me landing clearance right away, only asking that if I still had battery power when entering, they would like to hear from me.
With the precautions and good weather, I regard the risk as quite acceptable, almost the same as for normal flying. Hand propping was probably the riskiest part.
All equipment was working at the time of departure.
Pilot_DAR wrote:
If the pilot understand the systems well…
Well, obviously in the cases where it isn’t safe then it isn’t safe. But that wasn’t the point. The point was that there is no blanket ban in Europe for flying with an inoperative system even if you have no MEL. I have no idea about North America.
There are also limitations in aircraft POH, the DA40NG has electric ignition with FADEC engine which would be fun without a battery, the main battery may gives 30min and backup emergency battery about another 30min, if you plug backup battery it means land ASAP and will not fly again until an engineer sees the aircraft, same for fuel emergency transfer if you break-glass and cross-feed, you are grounded for next flight !
On aircraft types with “engine mags” the whole flight will be OCAS in good VMC, maybe in landing configuration on VFR MSA, otherwise one may need to switch his radio ON across borders or when jets are around 
for aircraft with electric fuel/flaps/gear, I expect any transition training to include discussion on fuel burn and landing without flaps/gear or manual/emergency extensions
The other problem is most GA maintenance facilities when you are flying away are inside CAS airports
Yes Ibra, that’s the link, thanks.
Airborne_Again wrote:
So the question is if the system is “required for the intended flight”
The first questions will be what is the intended flight, ’cause no matter how short, there will be an expectation of the VFR reserve added to the duration of the original intended flight. Knowledgeable pilots know that the design requirement will provide cautious operation for 30 minutes on the battery. And that 30 minutes could be your reserve, leaving a well planned flight having no electrical reserve.
If the pilot understand the systems well, the pilot would know that any aircraft with a fuel pump will have a second electrical fuel pump, and that would be in the seriously endangers flight category during an overshoot during the reserve portion of the flight. Similarly electric flaps or landing gear. So I’d have trouble accepting dispatch of an airplane with an electric fuel pump/flaps/gear, and an inoperative alternator, for anything more than a very brief “hop” flight. For a very simple day VFR only airplane with a minimum electrical system, and only the starter running off the battery, I would agree that you could get airborne, and turn off the master, and fly as long as you like.
Pilot_DAR wrote:
Technically, with no minimum equipement list, you have no argument that you may depart with an inoperative system. So, if you’re going to, you best be very confident that a secondary failure resulting from your decision won’t attract more attention to what you did!
According to EASA rules you don’t necessarily need a MEL.
NCO.IDE.A.105 Minimum equipment for flight
A flight shall not be commenced when any of the aeroplane instruments, items of equipment or functions required for the intended flight are inoperative or missing, unless:
(a) the aeroplane is operated in accordance with the MEL, if established; or
(b) the aeroplane is subject to a permit to fly issued in accordance with the applicable airworthiness requirements.
So the question is if the system is “required for the intended flight”. Also
ML.A.403 Aircraft defects
(a) Any aircraft defect that seriously endangers the flight safety shall be rectified before further flight.
(b) The following persons may decide that a defect does not seriously endanger flight safety, and may defer it accordingly:
(1) the pilot in respect of defects affecting non-required aircraft equipment;
(2) the pilot, when using the minimum equipment list, in respect of defects affecting required aircraft equipment — otherwise, these defects may only be deferred by authorised certifying staff;
(3) the pilot in respect of defects other than those referred to in points (b)(1) and (b)(2) if all the following conditions are met:
(i) the aircraft is operated under Annex VII to Regulation(EU) No 965/2012 (Part-NCO) or, in the case of balloons or sailplanes, not operated under Subpart-ADD of Annex II (Part-BOP) to Regulation (EU) 2018/395 or not following Subpart DEC of Annex II (Part-SAO) to Regulation (EU) 2018/1976;
(ii) the pilot defers the defect with the agreement of the aircraft owner or, if applicable, of the contracted CAMO or CAO;
(4) the appropriately qualified certifying staff in respect of other defects than those referred to in points (b)(1) and (b)(2), where the conditions referred to in point 3(i) and (ii) are not met.
So here the questions is if the defect “seriously endagers flight safety”. I would argue in the case of a VFR flight where you have planned in advance for how to safely conclude the flight given possibility of loss of electrical power, a dubious alternator is not a defect that seriously endangers flight safety.
As Peter says, assuming that the belt is intact. ‘Cause if it’s not, you have to remove the prop to replace the belt, and that’s a bigger job. To reduce the urgency of this when I’m in the bush with my Lycoming, I carry this kind of belt:
https://www.myford.co.uk/acatalog/A—-SECTION-LINK-V-BELTING-FOR-THE-HEADSTOCK-DRIVE—70090-1405.html
It can be “built” around the ring gear pulley, and It’ll get me home.
Otherwise, you have understand the electrical load analysis for your plane. When I did the research on a factory Cessna Grand Caravan for battery only operation, in accordance with the guidance for VFR day flying, the battery would provide 30.49 minutes of electrical power, where 30.0 minutes is the requirement – not much reserve beyond the requirement there!
Technically, with no minimum equipement list, you have no argument that you may depart with an inoperative system. So, if you’re going to, you best be very confident that a secondary failure resulting from your decision won’t attract more attention to what you did!
During my helicopter training, while I was lifting out of a confined area (an exercise), the instructor simulated an alternator failure by pressing and illuminating the press to test of the alternator light. I acknowledged that alternator failure, continued picking up, and headed back toward the airport, just a mile away…. “What are you doing?” questioned my instructor with a shocked expression… “I’m returning to the airport with a failed alternator, ‘cause I’m sure not going to put back down into a hole in the bush, and shut down, to have the maintenance guy lug his toolbox through the bush, cursing me the whole way!”. Well… it seems I missed the point. The point of the exercise was to have me land back into the confined area. So, into the hole again. This time, as I picked up, transmission chip light – yeah, that one I’m putting back into the hole for! It seemed that I understood a little too much about the helicopter’s systems, knowing that I did not need the alternator for a mile flight home!
Yes, I have departed an airplane with a failed alternator.
