Fuel sampling and trim runaways

Voiceover: 00:12

Welcome to the General Aviation podcast from the UK Civil Aviation Authority.

Billie Winwood: 00:22

Hello and welcome to the CAA General Aviation podcast. I'm Billie Winwood, and I'll be your host today. I'm speaking to some of my General Aviation policy team today. Welcome to Ed Bellamy and Jordan Bridge. Today, we want to talk to you about two safety issues that we want to bring to the attention of the GA community. They are trim runaways and fuel contamination and sampling. Both of these issues can have real consequences if not dealt with properly. So let's unpack them both and hear about what pilots can do in both scenarios. So Ed, you're going to be talking to us about trim runaways. For pilots who've never experienced it, what exactly is a trim runaway?

Ed Bellamy: 00:59

So I think it's worth just briefly refreshing ourselves on what trim in an aircraft does. So the trim system, which is typically a supplementary control surface or a mechanical device such as a spring, is there to essentially rebalance the bike control forces across the range and speed attitudes that you might fly at. So when you pitch up or accelerate for example, in an aircraft, that typically means your control forces as felt on the column will change, and the trim is there to essentially dial that out such that you're not going to have to hold any continuous pressure in that new attitude or speed. So the issue arises in terms of trim runaway when that device or surface essentially moves undesirably continuously to the point where it may cause control difficulties. So for example, the trim tab surface might move to one extremity or the others, giving you an extreme pitch up or pitch down scenario. This can occur for a variety of reasons so we're typically talking about electric trim systems here, although I guess it's possible for some kind of fault to occur to a mechanical one as well, but normally it would be a stuck switch or some faulty wiring, for example, that might cause the trim screw to move continuously. So perhaps a problem with the motor that drives the trim system, or it could be pilot error. So for example, touching the trim switch inadvertently, or knocking a circuit breaker or button, for example.

Billie Winwood: 02:29

Ok and how can a pilot recognize a trim run away? Are there any early clues that something isn't right?

Ed Bellamy: 02:34

So you might see a change in in pitch, because the trim is obviously about the pitch of the aircraft. Typically, I mean, you'll have a you'll often have a rudder trim as as well, or even an aileron trim. But the we're primarily talking here about the pitch trim system. So the aircraft might start pitching up or pitching down in an uncommanded fashion. And if you're hand flying, there'll be some control forces, unexpected control forces associated with that as well. You might see the trim wheel moving by itself, and if the autopilot is engaged, you might have some kind of light or other warning on your annunciator telling you that the trim desired by the autopilot system is not being engaged correctly.

Billie Winwood: 03:20

Okay, so a few early clues there that people can look out for. But how quickly can a trim issue escalate if a pilot doesn't react.

Ed Bellamy: 03:27

So potentially, very quickly indeed, even in a relatively small light aircraft, if you get a full nose down trim runaway that become could become uncontrollable very quickly indeed. And we've had several accidents as a result of that.

Billie Winwood: 03:42

So what's the first step when you suspect a trim runaway? What should pilots be doing?

Ed Bellamy: 03:47

So you should always be familiar, if you have electric trim, with the pilot's operating handbook procedure for dealing with any trim related abnormal scenarios. But typically, if the auto pilot is engaged, for example, you want to disengage that. Or if you're hand flying and you detect the trim running away, you need to disable the electric trim so that the servo for the trim wheel is denied power. And you typically do that by pulling the circuit breaker or whatever other button is associated with your system.

Billie Winwood: 04:20

Okay, before we move on to Jordan, Ed, is there anything else you think pilots should know about trim runaways?

Ed Bellamy: 04:25

So I think it's just really important to know your aircraft. Know if you have an autopilot, know how the how the system works, and all the abnormal procedures associated with that, practice touch drills in the aircraft, such that you know where the circuit breaker is for example. If a circuit breaker doesn't have a collar on it to to identify it quickly, then consider installing one, and just be prepared, like in any non normal scenario in aviation, prior practice is very important.

Billie Winwood: 04:55

Thanks for going over this issue, Ed and I know there's more to come from the CAA on this soon in a new Safety Sense Leaflet, which will give people more information. So do keep your eyes out for that, and make sure you're signed up to our SkyWise alerts channel so you know when it's published. Now over to you, Jordan, fuel contamination, this can be a big issue, and pilots should know how to sample fuel correctly. So tell us. Why does fuel sampling matter in General Aviation?

Jordan Bridge: 05:18

Fuel sampling is a critical part of the pre flight checks on any flight you're going to do, and sampling properly can really help prevent what could be a tragic accident if things were to go wrong and with contamination of the fuel with water or other debris. It might not actually prevent the aircraft from starting or even taxiing about but it could later lead to a sudden engine power issue during a critical phase of flight; may that be the initial takeoff roll or even the initial climb out, where this issue may arise. This actually happened to me a few years ago, though, thankfully, in my case, I landed safely. There are three primary sources for contaminated fuel that we're going to focus on today, and that may be an issue with the filler neck or the seal, which may allow contamination to seep in, maybe after a heavy period of rain, condensation within the tank, or maybe even contaminated fuel supply from the airfield that you're collecting from.

Billie Winwood: 06:14

Okay, thanks. So walk us through the correct fuel sampling process. What should a pilot be seeing or doing?

Jordan Bridge: 06:19

So firstly, you should always follow what is in your flight manual or POH. That's really important, because they're going to be specific items for your aircraft. But on a more general point, before sampling as you approach the aircraft, you should be sure that all of the fuel caps and covers that you expect to be installed are secured properly before and after you complete your pre flight checks. It's very easy to have a look in the tank and check the contents, but make sure that that fuel filler cap is locked again as you walk away. Perhaps allow the fuel to settle as well. Maybe sort of 10 to 15 minutes after refuelling, that just gives the time for the fuel to settle. Also gently rock the wings. This ensures that any trapped contaminants, water or sediment, can be dislodged, so that nothing is masked when you do your fuel sample. Okay, so now for the sampling itself. So drain every sumping point of a good amount. You should make sure that you're draining the sumping points which are specified in your flight manual or POH, there may be several across the aircraft. Once you've got your sample, visually inspect your sample in good light with a good contrast as well. Look for the colour and check it against the expectation. Know what colour your fuel type should be. Afgas, 100 LL, for example, is light blue. Jet A one may be clear to straw coloured. Other fuel types may have different colours too. So make sure you are absolutely firm on what colour fuel type you're expecting to see. Look for particles or debris. Have a look at separation as well. Water and fuel will separate with fuel floating on top. However, this may differ if you've got potentially mo gas or another type which may have some ethanol in it. Think as well. Could you have pulled a full sample of water? We recently saw a fatal accident where that took place, and although the smell smelt like AV gas, in fact, it's just because that that fuel sampling jar had been used many hundreds of times with AV gas that it just had that aroma. So it's important to check make sure that you actually have not just pulled a full sample of water. You can do that potentially by doing an evaporation test, maybe just put a bit of AV gas onto a rag, for example. AV gas will evaporate quite quickly. Or if it's poured onto the ground, it will evaporate quickly as well. UL 91 or 94 will act similar to AV gas, Mo gas and Jet A one will evaporate, but probably more slowly and may leave an oily residue. Water evaporates more slowly than that. Think, as well as I mentioned about checking for the right fuel, could it be the wrong fuel type in the aircraft? Have a look. Is there anything unusual that you haven't spotted before? Have you confirmed with a fueller what fuel type you've collected? Have a look at your receipts. Have a look at what you've been expecting. And don't forget, after you've taken on a large amount of fuel, you should sample again.

Billie Winwood: 09:07

Ok, thanks, Jordan, that's all really helpful. So if someone were to find contamination, what's the next plan of action?

Jordan Bridge: 09:14

So if contamination is found at your sample, you should continue to drain until clear, continually also rocking the wings as well, to try and dislodge any other contaminants that may be present and keep sampling. If, after a few samples, you're still not getting anywhere, you should really speak to your maintenance organisation so that you can potentially put this down as a defect and get it investigated.

Billie Winwood: 09:37

And do you have any top tips or common mistakes that people can avoid?

Jordan Bridge: 09:41

It's easy to get rushed when doing our pre flight checks. Potentially we're running a bit late, or we've got a slot that we're expecting to get into for a fly in, or something like that. And we cannot do all of the sampling points, so make sure that you're sampling every single sample point that the aircraft specifies, in the POH or in the flight manual. Not sampling after fuelling. Now, you might have sampled at the beginning of the day, but if you've picked up several bits of fuel throughout your journey, you don't necessarily know what quality fuel you've picked up, so it's a really good idea to make sure you sample. Misfuelling, making sure that if you're going to a self-service pump, for example, that you've picked up the right fuel type and that you haven't put it in a fuel type you're not expecting. It's also important to have some environmental considerations too. So discard your samples properly into a waste bin or in a designated area. Sampling too quickly after refuelling may not also give you the result you're expecting, and also not checking the fuel caps are secure before and after flight are also a potential risk of contamination.

Billie Winwood: 10:41

Thanks, Jordan. Is there anything else you think pilots should know about fuel contamination and sampling?

Jordan Bridge: 10:47

The CAA has a wide variety of safety material with our Safety Sense leaflets and the Skyway code, and we are shortly to update Safety Sense leaflet number 28 for fuel handling and storage to include more detail on fuel sampling. So keep an eye out for that, and we'll be publishing that shortly, and a SkyWise will go out to the community.

Billie Winwood: 11:05

So make sure you're signed up to SkyWise to get those alerts. Okay, thanks, Ed and Jordan, just to recap before the end of the podcast, Ed, any key takeaways that you just want to remind pilots about on trim runaways.

Ed Bellamy: 11:17

So if you do have an electric trim in your aircraft and or an autopilot, be sure that the system is maintained correctly, and have an understanding of the two systems, how they work and potentially how they work together if that's the case. During flight, be aware of any unexpected pitch or control force changes that might indicate that the trim system is malfunctioning. And if you do have an autopilot, again, understand how a trim failure might affect the operation of the autopilot, but most importantly, just know the non normal procedures for your aircraft. Be sure that the electric trim circuit breaker is identified and that you know how to respond appropriately. Should you encounter a pitch trim runaway.

Billie Winwood: 11:58

Okay, thanks, Ed. And what about you? Jordan, any final takeaways that you want to remind people of.

Jordan Bridge: 12:03

So fuel sampling is probably one of the most important checks you do. So take your time to take consistent, thorough fuel sampling checks before flight. Follow your flight manual or pilot operating handbook, and if there's any doubt as to the quality of the fuel, take further samples or consider speaking to a maintenance organisation.

Billie Winwood: 12:23

Thank you to Ed and Jordan for your time today, I hope that pilots have found this a useful recap on very important safety information, especially as we start to see the weather improve and days get longer, plenty more of us will be out flying now that spring is here. As mentioned, we're updating our Safety Sense leaflets regularly, so make sure you're signed up to our SkyWise alert system so that you have notification of when these are released, and if you have any questions about the topics we've discussed today or anything else, please do get in touch with us at GApodcast@caa.co.uk.

Voiceover: 12:58

Thanks for listening. This is the CAA General Aviation podcast.