Auto throttle & RA's
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Auto throttle & RA's
I seek opinions. On B733 in late 90's the QRH RA response was "disconnet A/P and follow pitch guidance..." On NG's the QRH instructions include disconnect A/T & A/P. I asked a Boeing pilot why the inclusion of A/T? It introduces a threat to speed control. I've seen it many times in the sim, and at lowish levels, where crews get a CLB RA and do not add enough thrust; get a CLB RA and go to full power and >2000fpm V/S; get a DESC RA and forget to add power once CLR of Conflict climbing back to assigned level. Imagine the mess you could get into at high levels.
The answer from Boeing was that they'd decided to standardise their philosopy of manual flight manual thrust. He was not immediately sympathetic to the thought that this was a threat to safe speed and V/S control. IMHO It is a high stress situation easiest handled by 2 hands on the control column for accurate pitch control and let A/T look after speed. He said he'd pass on the comment, but nothing heard yet.
What thoughts do you all have, and what are procedures on other models and types? Has the RA QRH procedure for B737 classic been changed to match NG's? Has any company decided to keep the old procedure?
The answer from Boeing was that they'd decided to standardise their philosopy of manual flight manual thrust. He was not immediately sympathetic to the thought that this was a threat to safe speed and V/S control. IMHO It is a high stress situation easiest handled by 2 hands on the control column for accurate pitch control and let A/T look after speed. He said he'd pass on the comment, but nothing heard yet.
What thoughts do you all have, and what are procedures on other models and types? Has the RA QRH procedure for B737 classic been changed to match NG's? Has any company decided to keep the old procedure?
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It could be argued that if played correctly the pitch change to react to the RA is gentle and not aggressive. In fact the FCTM states, in part: "RA maneuvers require only small pitch attitude change which should be accomplished smoothly and without delay. Properly executed, the RA maneuver is mild and does not require large or abrupt control movements. Remember that the passengers and flight attendants may not all be seated during this maneuver".
It takes only small manual pitch changes to cause quite significant auto-throttle movement if the AT is engaged. In turn this can exacerbate trim and stick force changes. In the simulator we occasionally see pilots flying a visual circuit by hand with AT engaged and it doesn't take long to see the AT moving up and down in response to minor speed variations caused by inaccurate height keeping. In a nutshell it makes for sloppy lazy technique.
There is one point to be considered in favour of leaving the AT engaged - despite the Boeing recommendation. And that is manual flying currency. With the almost total reliance on automation demanded by manufacturers, regulators and airline ops departments, pure manual flying skills inevitably decline. We see this when pilots disconnect the automatic pilot to practice an instrument approach.
Manual throttle skills degrade too - and that is understandable since autothrottles are used in almost every aspect of airline flying. Some pilots may feel leaving the AT engaged in an RA manoeuvre, is safer than leaving it to a startled pilot who is steeped in automatics is suddenly faced with manual flight and manual thrust lever operation during an RA. Of course for those pilots equally competent at automatics and full manual flight there is no problem with following the Boeing advice.
In a perfect world, all pilots should be equally competent at both automatics and manual flying skills. In reality, the increasing prevalence of Loss of Control accidents over the years, prove this to be far from true.
In my view, Boeing are right in recommending that manual flight means manual throttles as well.
It takes only small manual pitch changes to cause quite significant auto-throttle movement if the AT is engaged. In turn this can exacerbate trim and stick force changes. In the simulator we occasionally see pilots flying a visual circuit by hand with AT engaged and it doesn't take long to see the AT moving up and down in response to minor speed variations caused by inaccurate height keeping. In a nutshell it makes for sloppy lazy technique.
There is one point to be considered in favour of leaving the AT engaged - despite the Boeing recommendation. And that is manual flying currency. With the almost total reliance on automation demanded by manufacturers, regulators and airline ops departments, pure manual flying skills inevitably decline. We see this when pilots disconnect the automatic pilot to practice an instrument approach.
Manual throttle skills degrade too - and that is understandable since autothrottles are used in almost every aspect of airline flying. Some pilots may feel leaving the AT engaged in an RA manoeuvre, is safer than leaving it to a startled pilot who is steeped in automatics is suddenly faced with manual flight and manual thrust lever operation during an RA. Of course for those pilots equally competent at automatics and full manual flight there is no problem with following the Boeing advice.
In a perfect world, all pilots should be equally competent at both automatics and manual flying skills. In reality, the increasing prevalence of Loss of Control accidents over the years, prove this to be far from true.
In my view, Boeing are right in recommending that manual flight means manual throttles as well.
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In my view Boeing are right in recommending that manual flight means manual throttles as well.
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A37575: I understand your comments, and sadly some are relevant here. I know of a few operators who, due to fear that speed control in manual flight is not guaranteed, have an SOP that A/T should be left engaged until short finals, even when flying visual approaches; which are discouraged anyway. So we have an airline SOP to encourage max use of A/T when flying the most basic of manoeuvres - a visual circuit-, but which follows the NEW Boeing RA procedure. It just seems to me to be an unnecessary threat. There are many Boeing recommendations which are not followed by many operators.
Please keep them coming about other types. I'd be interested to find if this Boeing philosophy covers all their products.
Please keep them coming about other types. I'd be interested to find if this Boeing philosophy covers all their products.
