THOUGHTS ON ENGINE FAILURE DURING TURBOPROP SINGLE-ENGINE OPERATIONS
One of the worst scenarios we can face as aerial firefighters is an engine failure during low-level operations in a single-engine aircraft. For most operators and pilots, it remains a hazard that we can mitigate to an extent, but we might still end up accepting a good deal of residual risk.
As climbers rely on their ropes, or as base jumpers rely on their only parachute, our single-engine is our lifeline. There is no safety net, reserve chute, or backup engines as with twins. There are not many redundancies.
In those sports, and during a single-engine operation we either build trust in the material, or we don’t do it all.
Would you agree?
Is that true, though? Is that all there is to it?
As a pilot who regularly crosses the Atlantic and performs long ferry trips over areas where you would not want your prop to stop spinning, I would like to think we can do a lot more than just trust blindly, to reduce both the likelihood and severity of engine failures.
Let me show you what has worked for me so far in a few minutes!
First things first:
Any operation should start with an assessment of the hazards and risks involved
We start doing something, and we learn about hazards and risks along the way; I have seen it so many times, and I have done it myself.
Messing around with a trampoline set up in our backyards might only lead to bruises, a twisted arm, or a sore neck in most cases.
When it comes to other activities where we are prone to terminal trouble, we better do a good risk assessment and build our procedures around them before we begin.
Engine failures are not the exception and should be prominently displayed in hazard logs and risk assessments for low-level single-engine operations. Despite Pratt & Whitney’s reputation for reliability, the severity of a turbine malfunction in our low-level hazardous environment gets quite high if it occurs.
“The PT6 family is known for its reliability with an in-flight shutdown rate of 1 per 333,333 hours up to October 2003, 1 per 127,560 hours in 2005 in Canada, 1 per 333000 hours from 1963 to 2016, 1 per 651,126 hours over 12 months in 2016”
As we will see, despite the impressive statistics, there can be many other factors that influence an engine’s likelihood to quit or malfunction.
If we’ve been around for long enough, we may have experienced an engine malfunction, witnessed a colleague’s engine failure or at least heard of one.
During August 2022 we heard of a Conair Fireboss making a forced landing. According to the operator, “His skill and training as an aerial firefighting pilot under challenging circumstances enabled him to execute an exceptional emergency maneuver resulting in a safe outcome. He was faced with a problem with the engine, he went through his emergency procedures and put the aircraft down in such a way that he was able to walk away unharmed. Faced with a difficult bunch of decisions in a very, very short period, he did exceptionally well.”
A few years ago (2018), we saw a very similar accident, where an Airspray Fireboss performed a forced landing. The pilot also managed to get away walking. I had the opportunity to talk to the pilot who did an excellent job.
A great friend of mine had an FCU failure leading to an unresponsive engine back in 2012. The case is well documented and several recommendations were made by the investigation board, to Pratt & Whitney, and to PT6 Firefighting operators. He not only managed to safely land in 300m in the only open field he had within gliding distance, but he did so from only 900ft while performing all emergency procedures stated in the AFM, walking away with no injuries and leaving the aircraft with minor damages. After this accident, Pratt and Whitney turned an SB regarding a defective FCU part into a mandatory AD in 2015, where the part had to be replaced.
What a coincidence, when another very good friend of mine, did not have the same luck. In 2016 he had an FCU failure right after take off with really bad options for an emergency landing. According to an ongoing independent investigation, the organization had not performed the mandatory AD that the 2012 accident triggered. This time, it cost a life, leaving a lovely family behind.
I will stop more on the FCU, SB, AD, and the need for an override (MOR) later in the article.
Therefore, based on the above accidents and statistics, my personal take on probability and severity transferred to the classic matrix used in aviation:
Root Cause Analysis – WHY
If we want to get deep down to the root cause, we need to ask ourselves WHY.
Different methods can be used to understand the root causes, but the 5 whys I will show you is commonly used.
Several tips are provided below:
- Does not have to be five questions, however, the methodology describes that through five questions the answer will be found.
- Less than five may be ok.
- More than five rarely give more information.
- The questions shall follow the previous answer.
- May branch out into more root causes.
- Corrective actions must be possible.
Among the root causes or whys for engine failures could be:
- Fuel starvation
- Flameouts caused by environmental factors
- Turbine malfunctions
- FCU malfunctions
- Salty environments – corrosion
- Ineffective AMPs (Aircraft Maintenance Programs)
- Improper maintenance
- And pilot error
In this section, we will not go into detail about each one, but let’s concentrate a bit more on the first one; fuel shortages.
Let´s get some WHYs
Ok! Back on track:
Let´s go for the first “why”. An easy and quite common:
- Why did the aircraft crash? -> Because it ran out of fuel.
There have been many accidents to do with fuel starvation.
The following accident is an example of an AT802 used for fuel hauling in Alaska a few years ago. Five more cases are known to me personally, and I have heard about others.
What are the underlying causes of this particular root cause?
Why do we run out of fuel?
Let´s focus on this specific accident as a practical example.
- Second why(s) layer: Why did the aircraft run out of fuel?
Based on the findings of the NTSB report for this specific accident, inadequate pre-flight fuel planning, reliance on instruments without verifying the fuel level input, and improper decision-making to continue the flight while the low fuel light was illuminated.
- The third why (s) layer: Why did he perform inadequate fuel pre-flight planning, trusted the instruments without visual crosscheck and continued with a low fuel warning light?
The answer could be insufficient or inadequate procedures or others that we are unaware of (we are only guessing for the purpose of this exercise).
- A fourth why is: Why were there insufficient or inadequate procedures?
It may be due to a lack of training and mentorship.
- A fifth why (s) or layer would be: Why was there a lack of training and mentorship?
The lack of resources or busy upper managers may have contributed to the problem.
These are only a few examples, but there are more that I have experienced myself and that deal with hardware and improvable designs. As an example, some fuel systems do not have an anti-return valve or tank level valve, allowing fuel to migrate between wings and header tanks. Once we reach the 200L-300L range on either Air Tractor or Thrush, we could deliberately migrate fuel by flying uncoordinated and stop the engine within minutes. A fuel system shouldn’t allow this situation for aircraft that are easily uncoordinated, especially for those who are new to them. In older models, such as the Polish PZL-M18, level valves were used to balance wing tanks when imbalances occurred.
As we can see, we could continue to bring more whys or branches to the root cause.
Another method I like is Pareto, where there is always a small quantity of inputs that will produce a large number of results
Or the Fishbone diagram, which helps summarize and group all root causes.
Below is a potential example of the fishbone diagram for the engine failure case:
Once we have identified the root cause, we should define a corrective action plan and demonstrate corrective action implementation.
Let’s review each mitigation individually:
If I was you, I would definitely consider the following standards in your SOP.
- a) Fuel Management: Whether it is through newer fancier systems, such as the MVP Fuel Management page connected to the GPS, or a classic system as the one shown below, we should define an effective procedure in our SOPs regarding how we keep track of the fuel we have onboard and the fuel we will have after landing at our base or alternate.
We should also be clear about our minimum fuel policy after landing and define our maximum allowances for fuel imbalance when it is not defined in manuals. Here is an example of SPI´s, so when we download data from flights, we can spot deviations and pilot trends that could potentially lead to safety events.
- b) Higher cruising procedures: If you find yourself cruising from the fire to the airfield or to the scooping point (in the case of scoopers) lower than 1000 ft AGL, have another think and ask yourself why. Some of the reasons could be to avoid extra radio communication with airports, or sometimes, not even that, just an inherited habit from the Ag-flying or for the fun of it. Not worth it.
From 500ft our options are so limited that we might not even have time to turn into wind or avoid the worse obstacles ahead. Conversely, from 1000ft-1500ft we should have a good minute or even 2 if we are quick with procedures, to locate a less dramatic spot for a forced landing.
For ferries out of the firefighting operation, go as high as you can.
2-Competence Based Training:
A competence-based mission training program, focussing on deliberate practice, is the cornerstone of an effective training program. Below are some bullet ideas about it:
- Progress through training with less time constraints.
- A rated pilot could take 1 flight, a week, or a few months to be proficient on the mission.
- Standard to measure competence/performance.
- Specific goals. “What you do on those hours is more important than how many hours you do”.
- If we cannot measure it we cannot improve it.
- We all should achieve standard competence levels regardless of other factors as background or past achievements.
a) Actual flying:
The next table is an example with only the competence we are dealing with, engine failure + flameout during actual flying. For this specific operator, we had defined 60 different competencies for the Fireboss that the pilot should train on in order to demonstrate proficiency in any of them during the OPC.
b) Flight Simulator Training Devices
They work great, as this one from Conair. If you are not lucky enough to have access to one, or if you do and there is not a good training program in place where you can squeeze the most of it, a mock-up or cockpit ground time also works great to build muscle memory and internalize quick reactions. Visualizing costs no money and very little time, and if we have something while on standby, it’s time!
If we have to think about it and our hands don’t move as second nature, we won’t relight a flameout. Here is a video example with the Air Tractor, where you have 2 options, switching hands to hold the stick and reach to ignition with the right hand, or crossing your left hand to reach right side of the panel. Both work, but we need to have decided and practice in advance, when we have an emergency there is no time to figure it out.
We will return to the concept of “fast thinking mode” shortly.
Here is an example of a mock-up for the Thrush 710P, a great tool, easy to put together for operators and individuals willing to raise their own bar when at home or while on standby at the base. Notice how all the switches to do with emergencies as fuel pump, ignition, and starter are placed right next to the power quadrant where we will have our left hand. With the left hand, we can reach those in no time while we keep our right hand on the stick, not needing to lose time to switch hands.
c) Single Pilot CRM Training – Psychological aspects:
Not only the hard skills (technical) are relevant when dealing with emergencies.
Soft skills (non-technical) are crucial.
Here are some ideas on what should we look for when recruiting, and the standards to achieve:
In addition to those competencies to train and test during real or simulated flights, there is a lot we could do on the ground. It is not just about flying skills; it’s about developing a mindset that prioritizes safety, professionalism, and the well-being of all involved. A healthy mind equips pilots with the tools to handle the complex, dynamic, and often high-stress nature of aerial firefighting.
A well-trained mind can handle high-stress situations, make sound decisions, and respond effectively in emergencies.
We should learn to manage fear, panic, and anxiety, allowing us to tackle difficulties more effectively.
A stressor is a stressor, be it a non-expected situation in the air, or exposure to cold water, as shown in this video.
How we react to them, depends to a great extent on our training on stress exposure, in a controlled environment.
This idea links well with a concept called Hormesis. “The dose makes the poison.” What Paracelsus, a renowned Swiss chemist and scientist meant is that even lethal toxins can only harm our bodies in specific quantities. However, what he didn’t anticipate was the fact that his proverb about chemical stress would also apply to emotional and physical stress in the same way.
Here is a short video expanding on this important concept.
The psychological aspects are fascinating and well deserve an extra mini-chapter.
Other psychological aspects: Thinking, Fast and Slow
Airlines base their modus operandi on avoiding impulsive reactions – what they call the chimp brain (amygdala). The goal is to work on a plural and standard decision-making process (DODAR, DESIDE) supported by Critical Thinking & TEM.
You would be told to relax, observe, and confirm.
Take physical distance, breathe, relax muscles, and check the other crew member for inputs.
I agree on 100%. That is all great for those circumstances and has proven to be the way.
Having said that, In our line of work, as aerial firefighters situations can become critical in a matter of seconds. Not because we like to portray our activity as special, simply because we fly low most of the time and we are exposed to more hazards than in other forms of aviation. Mountain flying, single-engine, single-crew, smoke, wires, and other non-identified traffic are just a few.
For example, when you are about to drop your load and suddenly a helicopter appears out of nowhere, crossing your path, there is no time for careful analysis and following a checklist. We cannot afford to take a step back, lay down a yoga mat, breathe deeply for minutes, or seek further advice from a colleague next to us.
In these moments, our brains need to be trained to work quickly and accurately, almost like second nature, or else the consequences could be fatal as statistics prove.
These two examples I just brought, represent the sympathetic system vs the parasympathetic, or as Kahneman describes them, our two decision-making systems, system 1 (automatic- fast intuitive thinking) and system 2 (conscious – slow rational thinking).
In the accidents we have seen at the beginning of this article, where we have to deal with an engine failure, low-level and on our own, is the system 1 – fast thinking – working memory, the one that will save us, taking control during the emergency and assigning total priority to auto protection tasks.
One interesting exercise to test working memory and workload management is the Add 3 exercise. This exercise is based on Daniel Kahneman’s studies. If you want to test yourself and have some fun, do the maths at the pace shown in this video. And if you want to add some extra challenge, increase the number of digits and reduce the time between images.
Unless we are lucky enough to have a working memory of great capacity, we will be forced to work in an uncomfortable way. The problem comes when we try to use system 2 instead of system 1, overthinking with time constraints (as it could be a low-level single-crew engine failure), and the opposite, when we use system 1 to take shortcuts and biased decisions when we actually had enough time for system 2 to kick in and assess better (as it could be an abnormal situation at FL340 for a multi-crew operation).
I like to show students this this extreme video of low-level aerobatics and ask them which Nervous System he should adhere to and call if he wants to have chances of survival.
- Parasimpathetic – rational – calm – deep breaths – low heart rate – constricted pupils
- Simpathetic – high adrenalin – high cortisol – high heart rate – dilated pupils
He is clearly on Simpathetic – high adrenalin – high cortisol – high heart rate – dilated pupils.
Fight or fly mode.
Where do you think Aerial Firefighting stands?
From my perspective, somewhere in the middle between this video and the airlines.
As much as we like to standardize the operations and act calmly, due to the essence of the activity, there will always be a great part of sympathetic action.
The whole point is: Let’s not ban it and see it as something inherently negative, and instead, train it. A well-trained system 1 that recalls those automatic movements we have trained hundreds of times, as it could be to lower the nose to preserve energy during an engine failure while climbing, applying opposite rudder during a wing drop stall, or reaching the fuel pump and ignition switches instantly at the first signs of flameout, together with some doses of luck could mean the subtle difference between life and death.
If you are curious about Fast Thinking vs Slow Thinking, here is extended knowledge on the matter in the form of a short video.
3-FCU override installation:
I strongly believe that all operators using S.E.T’s low-level should have an FCU override as a backup. To support my statement, let us go back to the accident where my friend lost power and performed a successful forced landing. Based on the investigation, there are some crucial facts and recommendations that we should focus on.
As seen, there were a few documented accidents at that time starting with FCU problems. There is more to “PT6 turbines don’t fail”. The objective statistics shown on the related reported events are interesting data to support our beliefs inherited sayings or mantras.
Furthermore, the investigation highlights the need for an emergency power control system available, how it could have prevented several forced landings and how its use does not seem to be widespread among operators.
So why operators are still reluctant to install FCU overrides (MOR)? Is that a super expensive feature, or difficult to operate?
Good question to reflect on.
An FCU override is about 3000$ and straight forward to operate.
- It is crucial that pilots receive more education on the matter at hand. It is important to remember that turbines are also prone to failure, and statistically speaking, it is only a matter of time before we are affected. Therefore, we must adopt a defensive approach to flying, always keeping in mind that a failure can occur at any moment. To minimize the risk, we should fly low only when necessary and for as little time as possible. It is also important to have alternative landing spots in mind at all times.
- To ensure consistency and uniformity in our response to such situations, it is imperative that pilots undergo standardized training. A Flight Training Simulator Device (FTSD) is an excellent tool for this purpose, and with large fleets, there is no excuse for not having one.
- Let´s not forget the mind. A well-trained mind can handle high-stress situations, make sound decisions, and respond effectively in emergencies.
- We need management education to allocate resources for engine failure mitigation.
- We need to push manufacturers to make FCU override a standard feature. Safety features on cars are non-questionable nowadays. Here is a good example on this article.