The principles outlined in the IASA article and the posts in related threads advocating use of back stick are essentially correct. However, they do not consider the wide range of aircraft types, configuration, and variables that should be reviewed before a technique is recommended as a standard, let alone suggesting that crews could try it without such knowledge.
Braking effectiveness is improved by increasing weight on the main wheels, thus dumping lift with spoilers and lowering the nose to reduce AOA will provide major benefits. Similarly, so could raising the flap, but without comparing flap drag vs improved braking we cannot judge. Furthermore, the crew workload could be increased with change of technique, and based on the problems with selecting reverse cited in the article, that might not be a good course of action.
Further reduction in AOA (nose down stick) could increase the wheel force by producing ‘negative’ wing lift, but in those aircraft with high values of elevator power it could lighten the load on the main wheels or even worse break the air ground contact with detrimental effects.
Using back stick can generate increased wheel force with pitching moment, but this would be subject to the same variability of elevator power as forward stick i.e. it depends on the type. Other variables such as c of g, or engine / reverse configuration and their pitching moments also have to be considered.
A further contribution of back stick in increasing wheel load is to produce more ‘negative’ tail lift (part of the overall lift on the aircraft), but the amount generated also depends on aircraft type and configuration i.e. elevator vs all-flying tail. In proportion, the benefits of reduced tail lift may not be significant in comparison to correct spoiler operation and lowering the nose wheel. The tail forces will decrease as the aircraft slows down, thus this effect is also related to aircraft type and landing speeds, but also with crew workload immediately after touchdown where it is probably more important to confirm that spoilers have deployed, reverse is selected and max braking commenced.
One of the main problems with back stick is that the crew has no indication of the load on the wheels or the change that they are attempting to achieve; in some aircraft, the crew has no force feedback of elevator position. In other aircraft, it is possible to raise the nosewheel off the runway or reduce the load so that steering is ineffective. Noting that IASA suggested that crosswind performance would be improved, not that slipping sideways was eliminated, the article overlooked the yawing moment due to crosswind. Thus while the aircraft might not be as easily blown off the runway it could veer toward the runway edge and in some combinations the effects of yaw and side force are actually detrimental. (see the
Airbus reference 4.3mb re trading braking for steering). Rudder or nosewheel steering is required to counter yaw; the latter having reduced effectiveness and the former requiring additional crew vigilance and action, these are just some of the reasons why the crosswind limits are reduced (type dependant) on wet/contaminated runways.
The IASA article is potentially misleading by suggesting that crews “should be experienced in all valid stopping techniques”, implying that back stick is valid and approved. This is not the case in most aircraft types where the only approved technique is that published by the manufacturer.
The mental and physical effort in moving the stick rearwards might be much better used in checking that spoilers/reverse had deployed and that the feet are applying maximum brake pressure.
A safety organization such as IASA might have done better to take a wider view of the safety issue and seek to address some of the other causes. Whereas crew procedures and training are easy targets, (soft safety defenses), they are subject to human frailties, it is those harder safety boundaries that are usually the most effective.
The main problem in preventing overruns appears to originate from the contaminants on the runway. If the industry judges that the measurement of the contaminant and the relationship of those measurements with aircraft braking performance are unreliable, then IASA would be better advised to call for improvements in these areas or even to restrict operations to a clean runway operation only.