P&W JT8D-17 engines. Engine failure question
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P&W JT8D-17 engines. Engine failure question
During a discussion, the subject came up of reduced thrust take off's in the Boeing 737-200 equipped with the Pratt & Whitney JT8D-17 engines. The manufacturer's published Boeing 737-200 Pilot Training Manual, Date 1 February, 1982, had this to say under Abnormal/Emergency Procedures page 04.80.11:
"When making a reduced EPR take-off, reset operating engine to go-around thrust for additional performance margin, if desired".
I seem to recall from the early 1970's, that the FAA published an Operations Document on the principles of reduced thrust take-off procedures. Among other things, it stated that in event of an engine failure on take-off when conducting a reduced thrust take-off, resetting the live engine (s) to go-around thrust was prohibited.
I think that document was aimed at four engine jet transports such as the Boeing 707. If the aircraft was close to VMCA at lift-off, additional thrust applied to an outboard engine had the potential to cause a significant yaw and risk a VMCA problem at light weights.
The JT8D -17 was an upgraded and more powerful version of the JT8D-15 engines installed on Boeing 737 and Boeing 727 aircraft. I flew the JT8D-17 equipped Boeing 737-200 in Air Nauru in 1977 and I believe that operator was one of the first to operate the JT8D -17 and that was because the extra performance was needed for operating in the tropics.
A colleague of those days recalls that the AFM of the JT8D-17 fitted 737-200, stated that if an engine failed during a reduced thrust (EPR) take-off resetting the operating engine to go-around thrust was not permitted.
I don't recall that directive in either the AFM or any other associated Boeing manuals. I do, however remember clearly the FAA directive warning against increasing power on the live engine (s) during a reduced thrust take-off, but I am sure the directive only applied to the Boeing 707 or similar types for the reasons explained earlier.
Maybe this question is better posed in Pprune Tech Forum or even Aviation History and Nostalgia Forum?
Either way, I am curious if anyone could recall any restrictions on the JT8D-17 equipped Boeing 737-200, regarding increasing thrust on the live engine in event of an engine failure during reduced thrust take-off?
I am well aware that in theory, the take off performance calculations pertaining to reduced thrust take-off mean there should be no requirement to increase power on the remaining engine unless safety is being compromised. But my question is specifically about the JT8D-17 engine instructions / limitations.
The June 2015 Boeing 737 CL FCTM explains things thus:
"Since reduced thrust (ATM) takeoff must still comply with all regulatory takeoff performance requirements, it is not necessary to increase thrust beyond the reduced level on the operating engine in the event of an engine failure.
However, if more thrust is needed during an ATM takeoff, thrust on the operating engine may be increased to full rated thrust by manually advancing the thrust lever. This is because the takeoff speeds consider VMCG and VMCA at the full rated thrust.
"When making a reduced EPR take-off, reset operating engine to go-around thrust for additional performance margin, if desired".
I seem to recall from the early 1970's, that the FAA published an Operations Document on the principles of reduced thrust take-off procedures. Among other things, it stated that in event of an engine failure on take-off when conducting a reduced thrust take-off, resetting the live engine (s) to go-around thrust was prohibited.
I think that document was aimed at four engine jet transports such as the Boeing 707. If the aircraft was close to VMCA at lift-off, additional thrust applied to an outboard engine had the potential to cause a significant yaw and risk a VMCA problem at light weights.
The JT8D -17 was an upgraded and more powerful version of the JT8D-15 engines installed on Boeing 737 and Boeing 727 aircraft. I flew the JT8D-17 equipped Boeing 737-200 in Air Nauru in 1977 and I believe that operator was one of the first to operate the JT8D -17 and that was because the extra performance was needed for operating in the tropics.
A colleague of those days recalls that the AFM of the JT8D-17 fitted 737-200, stated that if an engine failed during a reduced thrust (EPR) take-off resetting the operating engine to go-around thrust was not permitted.
I don't recall that directive in either the AFM or any other associated Boeing manuals. I do, however remember clearly the FAA directive warning against increasing power on the live engine (s) during a reduced thrust take-off, but I am sure the directive only applied to the Boeing 707 or similar types for the reasons explained earlier.
Maybe this question is better posed in Pprune Tech Forum or even Aviation History and Nostalgia Forum?
Either way, I am curious if anyone could recall any restrictions on the JT8D-17 equipped Boeing 737-200, regarding increasing thrust on the live engine in event of an engine failure during reduced thrust take-off?
I am well aware that in theory, the take off performance calculations pertaining to reduced thrust take-off mean there should be no requirement to increase power on the remaining engine unless safety is being compromised. But my question is specifically about the JT8D-17 engine instructions / limitations.
The June 2015 Boeing 737 CL FCTM explains things thus:
"Since reduced thrust (ATM) takeoff must still comply with all regulatory takeoff performance requirements, it is not necessary to increase thrust beyond the reduced level on the operating engine in the event of an engine failure.
However, if more thrust is needed during an ATM takeoff, thrust on the operating engine may be increased to full rated thrust by manually advancing the thrust lever. This is because the takeoff speeds consider VMCG and VMCA at the full rated thrust.
"Since reduced thrust (ATM) takeoff must still comply with all regulatory takeoff performance requirements, it is not necessary to increase thrust beyond the reduced level on the operating engine in the event of an engine failure.
However, if more thrust is needed during an ATM takeoff, thrust on the operating engine may be increased to full rated thrust by manually advancing the thrust lever. This is because the takeoff speeds consider VMCG and VMCA at the full rated thrust.
However, if more thrust is needed during an ATM takeoff, thrust on the operating engine may be increased to full rated thrust by manually advancing the thrust lever. This is because the takeoff speeds consider VMCG and VMCA at the full rated thrust.
The Boeing Training Manual says "if desired."
As you say, if you're using assumed temperature you can add full thrust without any problems. However if you're using a fixed derate and were then to go to full non derated thrust there can be problems because your Vmcg and Vmca were based on the derate. Could that be what the Feds were talking about?
As you say, if you're using assumed temperature you can add full thrust without any problems. However if you're using a fixed derate and were then to go to full non derated thrust there can be problems because your Vmcg and Vmca were based on the derate. Could that be what the Feds were talking about?
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Can't speak specifically to the -17 as I haven't played in that variant's paddock.
Summarising the discussion to date -
(a) reduced thrust operations require AFM data to provide a quantitative basis for power/thrust setting.
(b) the Design Standards, from which the AFM evolves, require that there be no change in thrust setting unless via APR or similar systems. For example, FAR 25.111(c)(4). However, one needs to note that this relates to establishing certification (ie AFM) data only. As we are all aware, the operational rules can permit variations from the certification expectations.
(c) in general, there is no prohibition on the pilot's increasing thrust but that involves additional risks which should be avoided to the extent practicable. The main risks include
(i) directional control difficulties. This may/may not involve Vmc, per se, but we are all aware that introducing varying asymmetric thrust during a high workload OEI situation results in a very significant increase in pilot workload if control is to be maintained.
(ii) general increase in workload leading to a failure to maintain overall SA and the potential for loss of control due to, for instance, a breakdown in instrument scan.
(d) the fatal to VH-AAV some years ago provides useful reading. 35 years ago .. seems like yesterday ..
(e) sometimes the problems can relate to the state of the engines. I recall one turboprop fatal some years ago with which I was involved in the investigation .. the remaining engine was a very good performer and the pilots' increase in power following a problem with the other engine was very instrumental in the rapid departure and ground impact.
Summarising the discussion to date -
(a) reduced thrust operations require AFM data to provide a quantitative basis for power/thrust setting.
(b) the Design Standards, from which the AFM evolves, require that there be no change in thrust setting unless via APR or similar systems. For example, FAR 25.111(c)(4). However, one needs to note that this relates to establishing certification (ie AFM) data only. As we are all aware, the operational rules can permit variations from the certification expectations.
(c) in general, there is no prohibition on the pilot's increasing thrust but that involves additional risks which should be avoided to the extent practicable. The main risks include
(i) directional control difficulties. This may/may not involve Vmc, per se, but we are all aware that introducing varying asymmetric thrust during a high workload OEI situation results in a very significant increase in pilot workload if control is to be maintained.
(ii) general increase in workload leading to a failure to maintain overall SA and the potential for loss of control due to, for instance, a breakdown in instrument scan.
(d) the fatal to VH-AAV some years ago provides useful reading. 35 years ago .. seems like yesterday ..
(e) sometimes the problems can relate to the state of the engines. I recall one turboprop fatal some years ago with which I was involved in the investigation .. the remaining engine was a very good performer and the pilots' increase in power following a problem with the other engine was very instrumental in the rapid departure and ground impact.
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I believe that operator was one of the first to operate the JT8D -17 and that was because the extra performance was needed for operating in the tropics.
I believe the -17R version, like the JT8D 217 / 219 on the MD80 incorporated automatic power reserve increasing thrust automatically on the good engine in the event of a failure on the other one.
So there was no issue there !
These were fitted on later versions of the B727 and B737-200
So there was no issue there !
These were fitted on later versions of the B727 and B737-200
