By MR. BILL KROUSE, Ops RAMS Staff
The most important feature of the software used in the Military Flight Operations Quality Assurance (MFOQA) program is the capability to aggregately look at data for a fleet of aircraft; i.e., Big Data. MFOQA software is unbiased and nonjudgmental—it provides just the facts. MFOQA analysts use this software to sift through mountains of flight data collected by AMC aircraft, looking for events and trends that may lead to a mishap, which are then communicated to commanders and AMC Staff in order to modify potentially hazardous conditions and maneuvers. The analysis allows commanders to calculate their crews’ risks and affords commanders the capability to evaluate the challenges surrounding an en route airfield on their itinerary.
The software has highlighted many concerning trends across the MAF related to airspeed control. For example, it appears, and I emphasize “appears” because MFOQA software tells analysts what actually happened not why it happened, C-17 crews tend to drop airspeed out of their cross check as they transition to land. Also, it seems KC-135 crews have challenges transitioning from approach speed to threshold crossing speed when they are landing 40 flap. Not to be outdone, it looks like C-130J crews are slowing to 100 percent flap speed, while still configured at 50 percent flaps.
MFOQA analysis shows these airspeed control issues are not widespread; however, the ramification of these events have led to hard landings, runway excursions, and tail strikes. No loss of life, yet, but Class A and B mishaps have resulted. If your aviation professional gene is piqued, read on!
The C-17 is a technical wonder with a full suite of automation tools available to the crew to improve safety, reduce stress, and decrease human errors. The key is to understand how the automation functions and the assumptions made in the development of the systems. Aggregate analysis has shown C-17 crews have made significant strides in improving the stability of flying approaches using backside power techniques (Figure 1). The percentage of unstable approaches (UA) has dropped from the mid-twenties to single digits. As a single line, it is clear to see the improvements have plateaued (Figure 2) at around 9 percent. To meet the commercial UA norm of 2 percent, an in-depth look at all UAs was needed. Moving forward, MFOQA analysts examined the components of the UAs over the last year, finding airspeed control was the primary driver (Figure 3). Deeper analysis showed over a third of the UAs did not go unstable until the aircraft was below 300’ AGL (Figure 4). Of the crews that were unstable below 300’, over 85 percent were not following AMC directive to go around from UAs (Figure 5). The AMC staff does not believe the crew force is deliberately violating the command directive, leaving the only explanation that crews, including the pilot monitoring, are allowing airspeed to drop out of their cross check as they transition to land.
Consequently, AMC Staff is looking for automation upgrades, like adding a speed-deviation indication in the heads up display (HUD), but like any aircraft modification, it will take time (estimated delivery in 2024). In the meantime, the MFOQA analysis team is looking at the use of Pitch Attitude Command Attitude Hold (PACAH), when it is selected, how dynamic the flight path is when activated, the pitch angle when it is engaged, and trimming techniques used during approach. AMC Staff is coordinating an extensive analysis package, but until it hits the field, discuss the techniques of airspeed control with your fellow pilots and instructor teams to ensure airspeed does not drop out of your cross check. Only you can prevent loss of UA SA!
The KC-135 is to AMC like Queen Elizabeth II is to England: both are elegant, refined, and have been leading the way for a very long time. As a KC-135 pilot, I am a little biased. When I started flying the tanker, it was still designated as an A-Model water wagon. Due to the smaller engines and because of the required higher approach speed, we landed 40 percent flaps all the time thus improving the stability of the dihedral wing configuration, and improved spool-up time for go around capabilities. However, once we transitioned to the R-Model, power and spool-up time became minimized and focus was redirected at landing distances caused by the abundant residual thrust put out by the CFM-56 engines. With time, it appears the techniques for landing with 40 flaps went the way of the dodo bird. For the sake of fuel savings, AMC changed the KC-135 Dash-1, altering the primary flap setting for landing from 50 to 40 flap. As Figure 6 illustrates, this quasi-small change caused a spike in UA rates from 17.5 percent to 20.4 percent two months later.
The large fleet size of the KC-135 has a tendency to plateau changes, so a spike means something significant has occurred. MFOQA analysts dug deeper into this shift and noticed the location in the approach when crews are going unstable is during the transition from approach speed to threshold crossing speed. Figure 7 is a snapshot at 300’ for all approaches in a one year period showing 82.6 percent (40 flap) and 87.7 percent percent (40 flap) and 87.7 percent (50 flap) of crews are maintaining Vol 2 check-ride criteria for airspeed control. However, at 50’ approximate threshold crossing height (Figure 8), the percentage of crews on speed significantly drops to 55.7 percent for 40 flap, but only slightly dropped to 80.6 percent for 50 flap. The MFOQA CASE STUDY: KC-135 Threshold Speed Analysis (completed December 2015) provides all the details to support this article and can be found in your EFB. The numbers in the case study are a little different because it was completed December 2015. Figures 7 and 8 were created using flight data from a recent year, showing the issue is still alive and well.
Why the huge change between 40 flap and 50 flap landing configurations? Naysayers will say that MFOQA analysis is not taking into account wind corrections, like the additional airspeed crews are required to hold for mean ground reference speed. I counter with the fact that Figures 7 and 8 are the same approaches so whatever speed correction was added to the approaches in Figure 7 is probably the same amount added to the approaches in Figure 8. Discussions among the AMC Staff stressed there was little instruction in the way of Tactics, Techniques, and Procedures Guidance (AFTTP 3-3.KC-135) available as of November 2012 for adapting landing techniques for the new flap setting. The AMC Staff requested Boeing’s assistance to review two techniques for landing 40 flap. Boeing’s reply, Response to Inquiry (RTI) #246, included pros and cons.
1. Pull power to idle early (well before runway threshold), and let the aircraft decelerate with engines at flight idle all the way through touchdown.
The Boeing RTI also stated a single smooth reduction in power to idle to cross the threshold at threshold speed would likely lead to the most stabilized approach.
2. Reduce speed to Vth, and then add power to hold that speed until reaching threshold, followed by pulling power and setting the landing as one would in a 50 flap landing.
The Boeing RTI added that setting threshold speed at some point prior to the threshold would require a power reduction to idle 50’ above the runway and a corresponding adjustment to pitch to keep the nose from pitching down.
Using the Boeing RTI, AMC Staff updated the AFTTP 3-3 as follows:
40-degree flaps – (1) Pull power to idle when HAT equals fuel weight plus 100 feet (example, 20,000 lbs. of fuel, pull power at 120 feet, (2) crossing 500 feet HAT, adjust power to cross the threshold at target threshold speed. Accomplish a normal flare and landing. It is important to manage aircraft energy with reference to winds, gross weight, available thrust, and aircraft speed trend.
Unfortunately, MFOQA shows little to no change in the approach stability rate. This issue is still open and requires further discussion.
If you were impressed by the KC-135’s longevity, the C-130 is the longest continuously produced military aircraft (over 60 years), with the updated Lockheed Martin C-130J Super Hercules currently being produced. Since 1956, the Herc has participated in almost every military, civilian, and humanitarian relief mission that the United States has been involved in—the true definition of a work horse! As with the C-17 and KC-135, MFOQA analysis has highlighted an airspeed control issue with the C-130J. Aggregate analysis indicates many C-130J crews are slowing to 100 percent flap approach speeds, and even further to 100 percent threshold speeds prior to lowering the flaps to 100 percent.
According to T.O. 1C-130(W)J-1, pg. 2A-62, during a visual approach, “maintain no lower than approach speed for the existing flaps setting.” By slowing to 100 percent Flap Threshold Speed (VTHR) while still configured at 50 percent flap, crews are disregarding published procedures, thereby assuming an increased level of risk. Additionally, although rare, some crews are even failing to lower the flaps to 100 percent prior to touchdown. Detailed MFOQA analysis, coupled with feedback from the field, suggests the reason for the high number of “speed slow” events was a widespread C-130J flying community technique of slowing to 100 percent flap VTHR, and at times as slow as Max Effort VTHR, while remaining at 50 percent flaps, and then selecting 100 percent flaps to avoid over-speeding the flaps—especially when at heavier gross weight (GW). Unfortunately, this technique has a tendency to bleed over into lighter GWs as well. This crew force technique most likely developed in reaction to a real or perceived threat of unit-level disciplinary action for over-speeding the flaps.
MFOQA analysis was also combined with C-130J mishap trend analysis, which identified “speed slow” in several recent “tail strikes.” Perhaps the most severe discovery was a Class B “tail strike” mishap that resulted from the crew slowing to Maximum Effort VTHR with 50 percent flaps selected and continued to land with 50 percent flaps resulting in a tail scrape with major structural damage. In support of the crew force, discussions among the AMC Staff highlighted that the existing flight manual and AFTTP 3-3.C-130J guidance does not definitively address the flap over-speed issue. Fortunately, the AMC Staff is working with Lockheed Martin to evaluate the flap limit airspeed and developing techniques to prevent over-speeding them. There is a great case study posted in your EFB that outlines all the sources, analysis assumptions and conclusions (MFOQA CASE STUDY: C-130J Speed Slow at 500’ Analysis – 16 Jan 18). While the AMC staff coordinates with Lockheed Martin and the C-130J SPO to address the flap speed limitations, it is important for crews to follow established T.O. to the best of their abilities.
In summary, MFOQA analyses show that AMC crews have steadily improved their skills for flying approaches, and it highlights speed control close to the ground as an issue for crews to focus on. The AMC Staff is at work to address this issue from a technique perspective and hardware upgrade. Look for changes in the near future. In the meantime, fly safe, forward your concerns through your safety office, and let us know what else out there is a threat to operations!