RB 211 EPR / ANTI ICE Questions
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RB 211 EPR / ANTI ICE Questions
Our 757 has RB211-535E4 engines with EEC control. Worst case scenario, a departure with Anti Ice required, but forgotten. Is it possible that the EPR probes could ice up (similar situation to Palm 90) and display erroneous values?
I am used to GE engines, where this was not a factor, as thrust is referenced primarily to N1. I know we used to compute a value back on the Pratt's on the 727 to cater for this scenario.
I have seen a chart for this engine from a previous operator that compares Takeoff N1 to EPR at various temperatures. This is not included in the present QRH. Not sure how it was developed, but to me, indicates this could happen.
Does the EEC prevent this from happening using other N values as a reference?
Many thanks in advance, as this was asked recently, and I don't have an answer.
I am used to GE engines, where this was not a factor, as thrust is referenced primarily to N1. I know we used to compute a value back on the Pratt's on the 727 to cater for this scenario.
I have seen a chart for this engine from a previous operator that compares Takeoff N1 to EPR at various temperatures. This is not included in the present QRH. Not sure how it was developed, but to me, indicates this could happen.
Does the EEC prevent this from happening using other N values as a reference?
Many thanks in advance, as this was asked recently, and I don't have an answer.
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Ant-ice as in Nacelle anti-ice is completely seperate to probe heat. Probe heat is generally automatic and a function of N speed signal. So EPR shouldn't be affected by forgetting to put anti-ice on.
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I thought about that, but there is no mention of EPR probes in the FCOM (only the Pitot's, Aux pitot's, AOA, and TAT).
If I remember back to the Pratt days, the EPR probe was deiced only when using Engine Anti Ice, and this was the problem in the Palm 90 accident.
It makes sense that EPR probe is automatically anti-iced, but I am hoping to find a reference.
Thanks
If I remember back to the Pratt days, the EPR probe was deiced only when using Engine Anti Ice, and this was the problem in the Palm 90 accident.
It makes sense that EPR probe is automatically anti-iced, but I am hoping to find a reference.
Thanks
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From the 757 Maintenance Manual
Cheers, Fargoo
E_N_G_I_N_E_ _P_R_O_B_E_ _H_E_A_T_ _-_ _D_E_S_C_R_I_P_T_I_O_N_ _A_N_D_ _O_P_E_R_A_T_I_O_N_
1 . G_e_n_e_r_a_l_
A. AIRPLANES WITH RB211-535C ENGINES;
Two engine probes (one for each engine) are pneumatically heated to
prevent erroneous readings due to ice conditions. Engine probe heat
system components consist of the engine probes.
B. AIRPLANES WITH RB211-535E4 ENGINES;
Two engine probes (one for each engine) are electrically heated to
prevent erroneous readings due to ice conditions. Engine probe heat
system components consist of the engine probes. System electrical power
comes from the main left and right 28v dc buses, and the main left and
right 115v ac buses. Circuit breakers are on overhead circuit breaker
panel P11.
C. The engine probes are identified as P1 probes and they will be referred
to as the engine probes in this procedure.
2 . C_o_m_p_o_n_e_n_t_ _D_e_t_a_i_l_s_ (Fig. 1)
A. Engine Probes
(1) One engine probe is located on the upper inside surface of the inlet
cowl. The probe measures total pressure in the inlet air stream
entering the engine LP compressor.
(a) AIRPLANES WITH RB211-535C ENGINES;
The probe is continuously heated by bleed air from the
precooler.
(b) AIRPLANES WITH RB211-535E4 ENGINES;
The probe is heated by an electrical heating element which
provides one level of heating. The heater uses 115v ac power.
3 . O_p_e_r_a_t_i_o_n_ (Fig. 2)
A. Functional Description
(1) AIRPLANES WITH RB211-535C ENGINES;
Engine probe heating is done pneumatically. The engine probes
receive anti-ice directly from a duct leading to the engine bleed
air precooler.
(2) AIRPLANES WITH RB211-535E4 ENGINES;
Engine probe heating is automatically controlled. This is done by
action of air/ground relays and engine out relays whose position
depends on outputs from proximity switches and engine speed cards.
1 . G_e_n_e_r_a_l_
A. AIRPLANES WITH RB211-535C ENGINES;
Two engine probes (one for each engine) are pneumatically heated to
prevent erroneous readings due to ice conditions. Engine probe heat
system components consist of the engine probes.
B. AIRPLANES WITH RB211-535E4 ENGINES;
Two engine probes (one for each engine) are electrically heated to
prevent erroneous readings due to ice conditions. Engine probe heat
system components consist of the engine probes. System electrical power
comes from the main left and right 28v dc buses, and the main left and
right 115v ac buses. Circuit breakers are on overhead circuit breaker
panel P11.
C. The engine probes are identified as P1 probes and they will be referred
to as the engine probes in this procedure.
2 . C_o_m_p_o_n_e_n_t_ _D_e_t_a_i_l_s_ (Fig. 1)
A. Engine Probes
(1) One engine probe is located on the upper inside surface of the inlet
cowl. The probe measures total pressure in the inlet air stream
entering the engine LP compressor.
(a) AIRPLANES WITH RB211-535C ENGINES;
The probe is continuously heated by bleed air from the
precooler.
(b) AIRPLANES WITH RB211-535E4 ENGINES;
The probe is heated by an electrical heating element which
provides one level of heating. The heater uses 115v ac power.
3 . O_p_e_r_a_t_i_o_n_ (Fig. 2)
A. Functional Description
(1) AIRPLANES WITH RB211-535C ENGINES;
Engine probe heating is done pneumatically. The engine probes
receive anti-ice directly from a duct leading to the engine bleed
air precooler.
(2) AIRPLANES WITH RB211-535E4 ENGINES;
Engine probe heating is automatically controlled. This is done by
action of air/ground relays and engine out relays whose position
depends on outputs from proximity switches and engine speed cards.
I was under the impression (I could be wrong here
) that the EEC controls used in todays world could accomodate erroneous EPR readings on takeoff by comparing between engines and synthensizing to obtain valid inputs to the electronic brains of the EEC for all engines.
) that the EEC controls used in todays world could accomodate erroneous EPR readings on takeoff by comparing between engines and synthensizing to obtain valid inputs to the electronic brains of the EEC for all engines.
