The Spiral Dive Question …
In a Spiral Dive, I’ve heard it said a pilot should reduce g-loading prior to rolling in an ‘over bank’. Does ‘over bank’ mean more than 90 degrees banked or does it include say 60-90 degrees of banking? The reason for the question is related to the Push-Power-Roll mantra … does it really apply in a spiral dive where the bank angle is less than 90 degrees? The Spiral Dive is a bank problem so shouldn’t it be primarily a roll with aileron and rudder to fix it, not ‘pushing’ first?
(Paraphrased from a comment left on the APS website by ‘Kriegler’)
Response on Unloading in a Spiral Dive
* The following response has been transferred from the APS online forum. Please leave your comments at the bottom of the page and please include your name and email address.
Hi Kriegler – Thank you for your question (for the purposes of this distribution, the APS Director of Flight Training & Standards has included a short video on the Spiral Dive below).
The Primary Control Strategy you are referring to (‘Push-Power-Roll mantra’ – we don’t call it a ‘Mantra’ as that is not technically its intent) is an upset recovery strategy. By saying ‘upset recovery strategy’ I mean it is a series of control applications necessary in a given flight condition (that has exceeded some predefined set of parameters that cue a pilot that an atypical control intervention is likely necessary) to mitigate the situation. The specifics of those parameters signaling the need for an intervention recovery strategy vary with the airplane’s limit load, pilot experience level and even the specifics of the flight condition (such as speed, pitch attitude, configuration and available altitude above ground). In the example of the spiral dive you mention it implies the airplane has exceeded it’s critical bank angle and the pilot is near, at or even beyond the limit load of the airplane through the use of traditional elevator management by load variation in an unsuccessful attempt to arrest the continuing altitude loss by indiscriminately ‘pulling’ on the control column. Pulling even harder, in an attempt to bring the nose up, often has little positive benefit in relation the desired outcome of ‘Recovery’.
Briefly, before getting into a few details, ‘yes’ the primary issue faced in a spiral dive is a lift-vector orientation problem. This primary issue ultimately needs to be mitigated by rolling the airplane to a wings level flight attitude. However, just because it is primarily a rolling (or lift-vector pointing) issue it does not mean the lowest risk and most effective method of re-orienting the lift vector starts with the roll itself although it is clearly urgent to get to it as soon as practicable. Let’s outline a few assumptions to be able to better clarify the meaning of that sentence …
Assumptions and General Concepts
Let’s assume the pilot has just passed critical bank in a Spiral Dive at a speed above maneuvering speed at the limit load of his/her airplane. The Critical Bank Angle is the bank angle, when above maneuvering speed (Va), where a limit load sustained pull is required to just maintain level flight. A good question would be ‘What is the critical bank angle of my airplane?’. The answer is ‘It depends’. Generally speaking, the Critical Bank Angle of a 3.8G-limited light normal category airplane is about 73 degrees at airspeeds above Va. However, the critical bank angle of a 2.5G-limited transport category airplane is about 66 degrees. Keep in mind, the available limit load of an airplane often varies with configuration so understand the Critical Bank Angle reduces as your available limit-load reduces. An example of this would be the available positive G limit load in an 2.5G airplane reducing to 2.0G once flaps are selected.
Alright, that’s all mildly interesting but does that mean those 66 degree and 73 degree bank angles are the bank angles you’re looking for to signal when an unload is required before rolling? Not during an established limit load pull they’re not. Why? Well, if the pilot just started rolling (while sustaining a limit load pull) then the inboard wing could exceed limit load by as much as 33%. This is usually compounded by the demonstrated tendency of untrained pilots, who are ‘pulling and rolling’ out of fear of the ground, to pull even harder than they were pulling prior to initiating the roll. Exceeding the limit load on a wing by more than 50% is a real threat to exceeding the airplane’s ultimate load where catastrophic failure protection can no longer be assumed or expected. Given these brief points, it should be evident that rushing to a ‘rolling pull’ would not be the lowest risk recovery strategy to safely mitigate this situation unless ground impact was an immediate threat as the ‘rolling pull’ recovery would induce an unjustified asymmetric load on the airplane above it’s limit load. As you can see, the pilot must unload, at least to some extent, even when the bank angle is as low as the critical bank angle to keep within the airplane’s limit load. So, in response to the original question: ‘What minimum bank angle does the pilot need to consider unloading the airplane prior to rolling the lift vector towards wings-level in a spiral dive recovery?’ The generalized response based on what we’ve discussed so far is: ‘The minimum bank angle signaling that an unload is likely a prudent primary control input prior to rolling towards level in a spiral dive is typically between 45 degrees and 60 degrees of bank. This bank angle varies based on the airplane’s design limits, the specifics of the situation and the airplane’s position on the speed curve in relation to maneuvering speed’.
NOTE TO READER: To this point discussing the ‘unload concept’ in a spiral dive scenario, we have only addressed some of the limit-load implications whereas there are several other reasons unloading has additional benefits in certain situations. This is one of the those ‘certain situations’. Unloading prior to rolling can further enhance the pilot’s ability to safely mitigate the lift-vector pointing problem. Without getting into detail here, the additional reasons to unload prior to rolling revolve around roll rate optimization and associated influences on resulting dive angle during the recovery. Unfortunately, a thorough discussion on those topics would extend this already long winded reply.
Sidebar: The historic focus of stall recovery (from ab initio flight training through to transport category type rating and recurrency training) has repeatedly emphasized minimizing altitude loss. As is the case for loss of control in-flight for commercial pilots, general aviation pilots need to understand that GA Loss of Control In-Flight (LOC-I) is the leading cause of fatalities for them as well (see chart to right). Nearly half of those fatal accidents begin with the aerodynamic stall. Thanks to the major manufacturers responding to the fatal consequences of mis-prioritizing altitude loss as ‘the’ most important consideration in a stall during training, stall recovery techniques and strategies are being upgraded throughout the aviation industry to give primary focus to regaining and maintaining aircraft control. If that seems like it should be obvious, it is not obvious to a pilot startled in an upset or stall event. Sadly, there are many fatal accidents (including very recent ones) where mis-prioritization of minimizing altitude loss as been identified as negative training. This is often characterized by the accident pilot(s) instinctively pulling back on the control column in a stall (and keeping it back) despite a litany of aerodynamic cues, stall warning cues and negative stability handling characteristics clearly identifying the situation as a stall … the stall must be fixed by reducing angle of attack irrespective of altitude, airspeed or flight attitude. Re-enter the ‘push’ or ‘unload’ concept once again …
SUMMARY: The last point I’d like to bring forward is encouragement for readers to consider participating in our online academic video training (click the Red Cross at the top of any of the website’s pages). This training is suited to pilots of all skill levels and takes much of the academic mystery out of the loss of control in-flight threat to pilots. One thing we’ve learned over the years from the 1000s of pilots we’ve trained is that loss of control questions can be quite diverse and responses often perceived as overwhelmingly complicated as one could conclude from just the beginnings of the brief explanation I’ve offered above. The power of being actively involved in a fully comprehensive upset prevention and recovery training program such as is offered by APS is to render a large amount of the complexities of loss of control in-flight, and its seemingly endless variations, into a compartmentalized series of strategies that can be applied effectively, simply and comprehensively. Most importantly, these strategies can be applied consistently even in a high-stress, time-critical startle situation characteristic of the majority of real world airplane upsets whether those upsets be pilot-induced, environmentally-induced or system-anomaly induced.
Kriegler, I hope this answered at least a portion of your question even though I made a few assumptions to keep the response brief. All aspects of spiral dive situations (and a wide diversity of even more complex scenarios) are fully addressed during APS on-site practical training and throughout our on-line training services.
Paul BJ Ransbury
APS Emergency Maneuver Training – President
UPRTA.org – Vice President, Global Integration
ICATEE.org – Co-Leader, Upset Training Analysis Development Team
- Under Mr. Ransbury’s direct management and supervision of both US-based and foreign academies, more than 4,000 professional jet pilots have been successfully trained in standardized upset prevention & recovery training techniques and mitigation strategies
- Former F/A-18 Hornet Fighter Pilot and Instructor
- Former Airbus A320 Airline Pilot
- Gold Seal Flight Instructor / Master CFI – Aerobatic
CFI / CFII / MEI / AGI