Why UPRT (real and not only simulated) and having a deep understanding of aerobatics are crucial for Aerial Firefighters
Non-specialized people will experience an accident as a tragedy, a shock, and a new painful reality. An unexpected black swan event.
Conversely, if you have been around for a while, in addition to feeling the pain and frustration, from an analytical perspective, you will soon correlate the accident with a few official reports of similar accidents, and will identify indicators potentially leading to the event.
It is rare that the circumstances throw us anything completely new after 60 years of aerial firefighting and at least 30 years of documented events. In most cases, it has already happened and someone has paid for it.
There is no doubt that learning from others is cheaper, both in terms of human lives and economics.
LOC-I: A classic in the business
Loss of control in flight (LOC-I) events are not an exception. We have seen many serious and fatal accidents while maneuvering and during the dropping phase.
Here’s a picture showing a framed sequence of an AT-802 just before it crashed in Spain in 2014 during a fatal accident involving a LOC-I:
The Investigation Board’s findings are summarized below:
This link will take you to the English version of the full report. There are quite a few takeaways we could implement, as individuals and as organizations.
An accident that occurred in Australia in 1998 during a demo flight is another classic example of LOC-I we should study to prevent them during aerial firefighting. While dropping the water, the aircraft lost control, entered an inverted spin, and crashed in front of the crowd.
Here is the crash video.:
And here is the link to the full report by the Australian ATSB.
A few takeaways, for anyone wanting to read the report, from crowd effect to the need for UPRT education.
With real-world examples like these, it is obvious that UPRT is an essential asset for the aerial firefighters’ toolbox, mainly to prevent, but also to recover from situations when an airplane unintentionally exceeds its normal envelope.
Despite the fact that we aren’t obligated to do it for a Class Rating, there are clear indicators that point us in that direction:
- We fly low-level, low visibility, hot-thin-turbulent air.
- The majority of the flight takes place near the stall.
- Our flights are conducted in tight mountainous terrain with increased traffic interaction.
Here are a few takeaways I would like us to start thinking about:
- Situational awareness and other soft skills are essential to conduct and lead this sort of operation.
- A deep understanding of aircraft flight envelopes and behavior is crucial for anticipating and staying ahead of the game.
- It is important to know how to prevent upsets in order to save lives. The more we know about what to do when faced with one, and, most importantly, what not to do, the better our chances are of surviving.
Our goal is to avoid stalling or causing structural damage
At the bottom of this article you will find some relevant and practical videos, that conclude most of the points. Before getting there, and to make the most of them, we should review a few important concepts:
As a first point, we should bring up the small speed window we have for the whole flight while firefighting.
While other forms of aviation allow the pilot to fly at speeds ranging from 140kts to more than 400kts (more than 300% difference), firefighting allows only a narrow window between stall speed and drop speed – Va.
Here is an example with the Fireboss showing stall speed at MTOW for varying bank angles:
As seen, the stall speed is 77Kts when the aircraft is straight and level. The dropping speed is 110-115Kts. Before, we were talking about differences of 300% between stall and cruising speeds in other aircraft, but now we are only talking about a difference of 50% between stall and cruising speeds.
As we can see from the table above, the stall speed dramatically increases with an increased bank, which reminds us that while firefighting we spend most of our time banking due to terrain, other traffic, obstacles, and evasive maneuvers.
High G forces are generated by exceeding dropping speed and Va. Often this occurs more in the beginning when pilots naturally avoid stalling due to the fear of a stall event while flying low level (a natural and understandable reaction to train and avoid).
Consider these points:
- Damage from overstressing the airframe could range from something that is not noticed during flight to a catastrophic in-flight failure.
- Fatigue in the metal can be difficult to detect.
- The structure of metals like aluminum makes them extremely strong, but once their bonds are broken, they are more prone to failure.
- Airframes may become weak as a result of stresses resulting from exceeding the limit load factor, resulting in catastrophic failures at some future time.
Considering the speed window we have and the flight load factor limits, we find ourselves in a kind of “Coffin Corner,” where we are at the mercy of stall on one side and structural limitations on the other.
Check this video to see a structural failure during dropping.
Refreshing Load factor
- The load factor increases at a terrific rate after a bank has reached 45° or 50°. Watch out for banking more than 45º as load factor and stall speeds go through the roof.
- The load factor for any aircraft in a coordinated level turn at 60° bank is 2 Gs, which is the load limit with flaps down for the Fireboss. At 60º banking, stall speed with flaps down is as much as 103Kts.
- The load factor in an 80° bank is 5.76 Gs!
- The wing must produce lift equal to these load factors if altitude is to be maintained.
- If we need to bank more than 45º, our setup is wrong and we should try better.
Here is an example of the normal range, structural damage area, and structural failure area.
Stalls and Spin
Before we refresh the stall-related concepts, let’s examine how our aircraft behaves by digging into manuals and looking at what experts have to say.
When we talk about experts’ opinions on the matter, we are talking about the Turn Smart video you have probably seen already. Whether you have watched it or not, please do it again. It is a great video merging aerobatic knowledge with Air Tractors that has probably saved quite a few lives.
While focused on Ag-Aviation this is an EXTREMELY valuable refresher for anyone who does low-altitude maneuvering. Handley began his career as an agricultural pilot before becoming an internationally recognized air show performer. In this video, he explains how to turn smart and what happens when an uncoordinated stall occurs.
In addition, if you want to learn more about the importance of coordinated flight for aerial firefighters as well as the “lost art” of tailwheel flying, then I strongly recommend you read this article.
Stalls bullet concepts
- It is a matter of AoA.
- A stalled wing can still produce lift, but at a lesser efficiency due to increased drag.
- From a firefighting perspective, we should be aware that even in a nose-down attitude and flyable airspeed we can inadvertently enter a stall event.
- There is a lot of value to the stall warning. During stall warnings, we must reduce back pressure on the stick to reduce AoA effectively.
Stall signs – Fireboss / Air Tractor – important!
- The stall warning first appears intermittently
- Secondly, the stall warning becomes constant.
- In third place, we reach the buffet.
- The fourth occurrence is the aircraft stalling and dropping.
The stall could be prevented by easing after pressure on the stick at any of the first stages if we load progressively and coordinated. We can, however, jump from phase 1 to phase 4 in a blink of an eye if we fly uncoordinated and abruptly.
Understanding Angle of attack
Angle of attack, or AoA, is the angle between the oncoming air, or relative wind, and a defined reference line.
We should have the following knowledge regarding AoA if Firefighting:
- When trailing edge devices (flaps and ailerons) are extended, critical AOA decreases.
- Stalls are always associated with high AOA.
- Stalls can occur at any attitude.
- Regardless of the airspeed, a stall can occur.
- A critical angle of attack is the angle that produces the maximum lift coefficient before an aerodynamic stall occurs.
- Whenever a stall occurs, it occurs at a critical AOA, but at different airspeeds
- In the Fireboss, an angle of attack indicator would be very helpful. Previously, we had one approved for our model, but the installation was discontinued.
- Flying a flotplane is commonly referred to as attitude flying, and stalling goes beyond speed considerations.
- Having a good understanding of how hard the wing is working regardless of its weight, flap setting, or load factor is important for aerial firefighting, and even more for scoopers.
- Here’s a video explaining the differences between stall warning and angle of attack, as well as how it affects floatplane flying.
Spins (Based on Air Tractor Manuals – P.A.R.E technique)
- Spins and stalls are both related to high angles of attack.
- During a spin, the airplane is turning around the Z axis, while it is possible for the airplane to stall indefinitely.
- Spin recovery techniques for this aircraft have not been fully investigated and can’t be established until the spinning characteristics of this aircraft are fully investigated. You are becoming a test pilot if you inadvertently spin, so follow these instructions:
- 1) POWER – Idle. : The torque of an engine producing power will make spin recovery more difficult.
- 2) AILERONS – Neutral. : Attempting to level the wings with aileron input can actually make the spin worse.
- 3) RUDDER – Apply to full opposite direction of spin. : If you have trouble determining which way the airplane is spinning, look at your turn coordinator, or turn needle, it will show you the direction.
- 4) ELEVATOR – Move fwd to decrease the angle of attack until the rotation stops.
- 5) RECOVER from dive. : Once you have completed the four previous steps, and the rotation stops, recover from the dive. The descent rate may be high and the airspeed can rapidly exceed the redline. Remember to neutralize the rudder after the rotation stops.
- Incipient spins are defined as a stalled condition where rotation is just starting. Anything less we define to be a stall or a wing drop stall which will require normal stall recovery. The incipient can be entered and practiced with students after they are proficient at stall recovery.
- As we mentioned previously, there is no possibility to recover from a spin while firefighting. Altitude is too low.
- Our best action is to know as much as we can about spin entry and aircraft behavior in the spin envelope.
Takeaways from Stalls and Spins
- As the flight envelope in Firefighting operations is performed close to the ground, recovery from a stall or a spin is more likely to be fatal due to a lack of space to recover.
- The most effective way to cope with an UPSET is not to let it develop, by being extremely familiar with stall and spin entry indicators.
- There is no need to bank more than 45º. That is plenty already.
- Deliberate practice will be our best resource to avoid UPSETS. See the 8´s on pylons exercise at the end of the article as a good example. There are other exercises to perform in order to be proficient in this specific competence.
- In our aircraft, we will perform all sorts of approved stalls a wing drops conservatively, with sufficient altitude to safely recover.
- In an aerobatic aircraft specifically, design and approved for aerobatics, we should become proficient at spins and UPRT in general.
- The following video shows how we practice stalls, incipient spins, wing drops during turns, and all sorts of spins, tailored to Firefighting.
Emergency hopper Jettison
- Although during spin recovery with sufficient height it is commonly taught to dump the hopper load as the very first action, the emergency hopper jettison procedure covers a broad variety of scenarios.
- As much as it is true that a heavily loaded aircraft might represent a big problem in an emergency, we must not get rid of it in a manner that could make the resulting situation even worse, especially when low level.
- Primary attention in an emergency must be focused on flying the airplane. So, if the airplane is in an upright position and we are aware of our attitude we should proceed with the jettison.
- If we are in an upset position and height allows, we could consider recovering first and jettison later. This way we are not doing the upset even worse.
- If we are stalling in a turn and while one wing is dropping (one more stalled than the other), and we drop half the weight of the aircraft, that sudden excess of lift while fully depressing one pedal, could make us do a snap roll or end up inverted!
- This could have been a contributing factor in a few LOC-I accidents.
Turn Radius and mountainous terrain
In addition to the illusions created while flying around mountains, such as false horizon or mountain relative scale, there are a few more factors to consider:
- The turn radius is a function of both bank angle and airspeed.
- If the bank angle is held constant and the airspeed is increased, the radius of the turn changes (increases).
- A higher airspeed causes the aircraft to travel through a longer arc due to a greater speed.
- An aircraft traveling at 120 knots is able to turn a 360° circle in a tighter radius than an aircraft traveling at 140 knots.
A practical example involving turn radius and mountainous terrain:
- Airspeed is the most influential factor in determining how much distance is required to turn. Many people have made the error of increasing their bank angle when a simple reduction in speed would have been sufficient, providing we won’t stall it.
- As seen before, the use of Flaps will reduce considerably the stall speed at a given bank angle. In the case of a 60º bank angle, which is the load limit for flaps down (2.0g) it reduces the stall speed from 109 kts to 103kts.
- Help yourself using flaps if needed to get through the turn while happy on energy. Doing so before the turn, will increase drag and reduce energy.
While the above examples are classics from basic aviation books, the following video shows a couple of real scoopings to reverse course with 700m (2300ft) available in the canyon, surrounded by terrain while firefighting and scooping from Douro River in Portugal.
With this video, I want to show not only a tight advanced maneuver, where all the above-mentioned concepts are applied to perform it:
-Coordinated flight at all times.
-Proactive energy management.
-Consistent setup. Use of fixed references to perform the maneuver. (Ref 1: Entry point / Ref-2: Decision point / Ref-3: Exit point)
-Speed, stall speed, banking, and load factor awareness.
-Stall indicators: Intermittent stall warning, continuos stall warning.
-Proactive use of flaps.
With the video, I also want to show how hard the environment is, especially for new pilots. It mixes wires, reduced visibility, obstacles, other vessels, more traffic, and mountainous terrain. Some of the most advanced scenarios we could face as Scooper pilots.
The mentoring process is crucial to introduce a pilot to those hazards, moreover in single-crew aircraft. There should be an experienced leader who has worked in the area before, able to reduce the workload for the rest of the group, giving more to them than taking from them. The mentor role.
Putting a new pilot, or worse, a pair of new pilots in such an environment sounds as unfair as negligent.
Last, I do not want to encourage pilots to perform tight turns. Conversely, I want to raise awareness of what is needed to perform them.
If operating in a confined space:
-We should know exactly where the threshold for our best performance is and our limits
-It is important to pick up clues and references to see how our current performance level fits. We need markers and metrics. Whether it is the scooping site dimensions, the turn radius available, or the dropping site, it is imperative to have an initial reference point we should consistently aim to, a decision point (where we continue or abort), and exit point.
-While these sorts of turns are the A-B-C for pilots with an agricultural background (where you can perform hundreds of those in a single day), they will be extremely challenging and exposed for the newer pilots, especially those without a stick and rudder background.
-Know your limits, and your margins, and plan accordingly. If does not feel right, do not try.
-Do not rush to take the lead if you are pushed to take that role. There is a lot going on in the front when leading, and a lot of specific expertise that takes years to come.
Training these maneuvers through deliberate practice – 8´s on pylons, a great exercise to see where we are
All this information might sound great and useful, but if we don´t practice it becomes useless with time. And if we don’t practice well it turns into wasted resources or busted safety margins.
While regular practice might include mindless repetitions, deliberate practice requires focused attention and is conducted with the specific goal of improving performance, under a purposeful and systematic approach.
While racking up hundreds of unstructured solo flights will help you learn a few things about the aircraft and its operation, it will not necessarily put you on the path to high-level piloting. And if you do not reach a high level of piloting, then you crash sooner or later. As simple as that.
Remember that the quality of your training can be as important as the quantity of your training. The number of hours you have amassed is not as significant as what you did on those hours.
The following exercise is an example of deliberate practice, with the goal of assessing a specific competence: turning performance at MTOW in a confined space. This transfers directly to operating in mountainous terrain or scooping in canyons.
Based on my standards and expectations as an instructor, the radius available in this example is 500m, and the distance available is 1000m for a full track reversal. As a reference, we should establish both vertical and horizontal limits using two pylons on the sea.
We can assess, and very quickly identify, whether the pilot is capable of maintaining coordinated flight at all times, proactive power management, and good environmental awareness (not too high, not too low, and within horizontal limits) during turns.
By looking out and scanning in, rather than the other way around, we will learn to fly using our sense of the pants. We also learn to listen and feel clues for the stall, and release back pressure when the stall warning becomes continuous instead of intermittent. As long as we don’t have an AoA indicator with a visual representation of the whole range, understanding the stages of the stall warning is crucial. Depending on where the wind comes from, we may need to tighten or ease the turn.
At this advanced stage, we would have practiced all UPRT maneuvers at altitude, in an aircraft certified for aerobatics, and all the stalls we could perform with conservative margins in our specific model. Before bringing it all down close to terrain or water, we should be very proficient with simple maneuvers such as 45º and 60º coordinated 360 turns.
This exercise also works great to identify other important soft skills, such as multitasking under pressure. In that cockpit, it gets really busy and demanding. Sometimes pilots collapse due to being unsuitable or needing more training. Some pilots remain as cold as ice while accurate in their technical skills, and this is a great indicator of a suitable profile.
During the recruitment process of new candidates, I perform this exercise or similar ones.
A recent painful accident
I would like to conclude this entry with a very relevant video. The simulation begins by showing the exact same real video we watched operating in Douro River, Portugal, along with the exact same scooping point. It continues with the simulation, based on the information provided by the investigation, of the unfortunate and tragic accident that happens a few kms away.
GPIAAF (Portuguese Accidents Investigation Board) has issued an Information Notice with the purpose of disclosing relevant facts about the fatal accident involving a Fireboss in Portugal last 15th of June.
Here is the link to the Information Notice.
This document contains provisional information and represents only a summary of the events as they stood at the time of writing, subject to change as the investigation proceeds. It is important not to fall into the hindsight bias in apportioning blame and liability, but rather to draw lessons that can be used to prevent similar accidents in the future. We should tread a fine line of respecting other colleagues involved while raising awareness to prevent similar accidents.
Knowing the pilot who suffered the accident, how thankful he was for the information this blog contains, and the value he saw in some of the posts, I imagine he would like to help others prevent a similar scenario.
R.I.P – André Serra. Rest assured we will learn from it and we will do our best for others not to go through the same.
And it is indeed helpful for pilots out there to have provisional information. We appreciate the Portuguese authorities’ prompt response. It’s a busy and challenging season in the aerial firefighting scene, so there might be some immediate lessons that can be learned to mitigate the hazards, as we have tried to describe.
Here is the image provided describing the accident, according to witnesses:
Video of the simulation:
These sorts of simulations are part of what we call Scenario Based Training. They can be used to analyze and compare, as I just did. But also to scout and build a mental map of the area you will have to work from. A useful tool.
Goggle Earth Pro, in addition to the simulation mode we have just seen, with similar speeds and climb performance to the ones we use, allows us to measure distances and profiles. This is useful to check areas we suspect we can be deployed beforehand, or as a debriefing tool if we want to measure our performance.
Although not perfect, this program is free, easy to use, and helps us put things into perspective.
While we wait for the final report, and there could be other contributing factors, so far we know it has been classified as LOC-I (Loss of control in flight) while maneuvering in a confined space. As long as the investigation has not been completed, we can only note it and learn from it the best we can, envisioning the worst-case scenario (more of the same happening), and get to the root cause.
U.P.R.T. is the main mitigation we can reach, and with this entry, I hope to have contributed to mitigating the probability of a similar event happening in the near future.
More than a year ago, I posted about the benefits that aerial firefighting operators will encounter by training their crew in actual aircraft for aerobatics, as well as how it will reduce the likelihood of LOC-I incidents.
A week ago, I spoke on training & safety, stating that a lack of UPRT skills has killed a few firefighting pilots:
Regardless of the regulatory framework (UPRT is not required for class ratings and firefighting), we should provide all possible safety tools to our frontline personnel, and we as individuals should push for them to come.
I do not believe on black swans and the unexpected.
I believe in metrics and indicators.
Hope it helps, and do not hesitate to reach out.
I am a Fireboss pilot, instructor, and examiner on the model. I have performed more than 15 seasons firefighting, and logged 7000 hrs in stick and rudder aircraft, of which 1500 are on the very specific model called Fireboss.
I admit my own biases influence me. Among these biases could be the hindsight bias; although I spend my days on the frontline, the truth this time is that I write these lines from the comfort of my home.
But as real as my biases (which we all fall into, with more or less awareness), is the fact that my modus operandi is governed by my values, life philosophy, and my professional ethics. One has to do what is right, not what is easy.
I own my standards, I consider I have the moral right to have an opinion. And I have the assertive right to change my mind and apologize if some of my statements are proven wrong or inaccurate.
I am financially independent of flying and organizations. I certainly don’t need to endorse products or ideas that I don’t firmly believe in.
I work globally as a consultant for the aerial firefighting industry, driven not by money, but by three fundamentals:
- The emotional imprint that my father left on me (aerial firefighter from the ’70s who died when I was 8).
- The feeling of having a purpose while protecting people and society.
- The self-imposed responsibility of leaving a legacy; a safer scenario to future generations.