FAIL SAFE MULTI-ENGINE TURBOPROP AIRFRAME THERMO-PNEUMATIC ANTI-ICING SYSTEMS

Abstract

Thermo-pneumatic anti-icing systems include port and starboard anti-icing subsystems operatively interconnecting heated engine bleed air discharged from port side and starboard side turboprop engines with port and starboard airfoils, respectively, associated with an aircraft to thereby provide in-flight anti-icing protection to the port and starboard airfoils, and an auxiliary power unit (APU) capable of discharging a supply of heated APU bleed air to the port and starboard anti-icing subsystems during an abnormal single engine or a single pneumatic bleed air operational condition. A controller may command respective port and starboard cross bleed valves to open and thereby allow the APU bleed air to be supplied to the one port or starboard anti-icing subsystem that is incapable of delivering heated engine bleed air from the port side turboprop engine or the starboard side turboprop engine, respectively. The port and starboard airfoils are thus each protected against inflight icing during the abnormal single engine or single pneumatic bleed air operational condition.

Claims

1. A thermo-pneumatic anti-icing system for a multiengine turboprop aircraft comprising: (i) port and starboard pneumatic bleed air subsystems adapted to provide a supply of heated engine bleed air discharged from port side and starboard side turboprop engines of the aircraft; (ii) port and starboard anti-icing subsystems operatively interconnecting the port and starboard pneumatic bleed air subsystems with port and starboard airfoils associated with the aircraft to thereby provide in-flight anti-icing protection to the port and starboard airfoils, respectively; (iii) an auxiliary power unit (APU) capable of discharging a supply of heated APU bleed air to the port and starboard anti-icing subsystems; (iv) normally closed port and starboard cross bleed valves XBV1 and XBV2 associated operatively with the port and starboard pneumatic bleed air subsystems and pneumatically connected to the APU so as to supply, when opened, heated APU bleed air to the port and starboard airfoils, respectively; and (v) a controller which issues a control signal to either the XBV1 or the XBV2 in response to a single engine operational condition wherein one of the port or starboard pneumatic bleed air subsystems is incapable of delivering heated engine bleed air from the port side turboprop engine or the starboard side turboprop engine, respectively, the control signal thereby respectively opening the XBV1 or the XBV2 and allow the APU bleed air to be supplied to the one of the port anti-icing subsystem or the starboard anti-icing subsystem that is incapable of delivering heated engine bleed air from the port side turboprop engine or the starboard side turboprop engine, respectively, whereby the port and starboard airfoils are each protected against inflight icing during the abnormal single engine anti-icing operational condition.

2. The system according to claim 1, wherein the port and starboard anti-icing subsystems comprise a port piccolo tube and a starboard piccolo tube which receive heated engine bleed air from the port side and starboard side turboprop engines supplied by the port and starboard pneumatic bleed air subsystems and direct the heated engine bleed air against an interior leading surface of port and starboard airfoils, respectively.

3. The system according to claim 2, wherein the APU comprises an APU bleed air supply line and port and starboard bleed air branch lines pneumatically connected to the APU bleed air supply line.

4. The system according to claim 3, wherein the XBV1 and XBV2 are operatively associated with the port and starboard bleed air branch lines so as to supply heated APU bleed air from the APU bleed air supply line when opened to the port and starboard piccolo tubes, respectively.

5. The system according to claim 1, wherein the port and starboard pneumatic bleed air subsystems include a port operating valve (PRSOV1) and a starboard operating valve (PRSOV2) connected operatively to the controller to controllably supply heated engine bleed air from the port side and starboard side engines to the port and starboard airfoils, respectively.

6. The system according to claim 2, further comprising port and starboard environmental control (ECS) packs pneumatically connected to the heated engine bleed air discharged from the port side and starboard side turboprop engines, respectively, for controlling at least one environmental condition within the aircraft.

7. The system according to claim 6, wherein the port and starboard pneumatic bleed air subsystems include port and starboard pneumatic branch lines upstream of the port and starboard ECS packs which are pneumatically connected to the port and starboard anti-icing subsystems, respectively.

8. The system according to claim 7, wherein the port and starboard anti-icing subsystems include port and starboard anti-icing valves operatively connected to the controller to control supply of heated engine bleed air from the port side and starboard side engines to the port and starboard piccolo tubes, respectively.

9. The system according to claim 7, wherein the controller controllably modulates the port and starboard anti-icing valves to maintain a substantially balanced supply of heated engine bleed air energy to the port and starboard piccolo tubes during the abnormal engine operating condition.

10. The system according to claim 9, wherein the controller includes data stored in non-volatile memory associated with mass flow curves of the port and starboard piccolo tubes, and modulates the port and starboard anti-icing valves according to the equation: $EB{A}_T\times EB{A}_F=APUB{A}_T\times APUB{A}_F,$ where EBA .sub.T and EBA.sub.F are the temperature (K) and flow (kg/s), respectively, of the bleed air from the normally operating engine and APUBA.sub.T and APUBA.sub.F are the temperature and flow, respectively, of the bleed air from the APU.

11. An aircraft which comprises: port and starboard side airfoils; port side and starboard side turboprop engines each being capable of discharging heated engine bleed air for in-flight anti-icing protection of the port and starboard airfoils, respectively; and the thermo-pneumatic anti-icing system according to claim 1 operatively interconnecting the heated engine bleed air to the port and starboard airfoils to protect the port and starboard airfoils against inflight icing.

Description

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[0017] The disclosed embodiments of the present invention will be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative embodiments in conjunction with the drawings of which:

[0018] FIG. 1 is schematic x-ray view of a multi-engine turboprop aircraft provided with a fail-safe thermo-pneumatic anti-icing system in accordance with an embodiment of the present invention; and

[0019] FIG. 2 is a detailed view of a typical wing leading edge employed in the system depicted in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0020] Accompanying FIG. 1 schematically depicts a multi-engine turboprop aircraft 10 provided with a thermo-pneumatic anti-icing system 20 having port and starboard side anti-icing subsystems 20.sub.PS and 20ss which are operatively associated with port and starboard pneumatic bleed subsystems 20.sub.PB and 20.sub.SB, respectively, in accordance with an embodiment of the present invention. As shown, the aircraft 10 includes a fuselage 12 with port and starboard wings 14a, 14b extending therefrom. The aircraft 10 is a multi-engine aircraft since it is provided with a port engine (Engine 1) and a starboard engine (Engine 2) each of which is operatively connected to the respective port and starboard pneumatic bleed subsystems 20.sub.PB and 20.sub.SB. As shown, the bleed air pneumatic circuitry of the port pneumatic bleed subsystem 20.sub.PB includes bleed air supply lines 16a1, 16a2 which supply heated bleed air from the port engine (Engine 1) while the starboard pneumatic bleed subsystem 20.sub.SB includes bleed air supply lines16b1, 16b2 which supply heated bleed air from the starboard engine (Engine 2). The bleed air from Engine 1 and Engine 2 is also supplied to an environmental control system (ECS) Pack 1 and ECS Pack 2 via bleed air supply lines 16a2 and 16b2, respectively, so as to control cabin environmental conditions (e.g., cabin air flow and temperature).

[0021] The port and starboard anti-icing subsystems 20.sub.PS and 20ss are provided with piccolo tubes 30a, 30b extending along the leading edges 32a, 32b of the port and starboard wings 14a, 14b and associated wing anti-ice valves (WAIV) identified as WAIV1 and WAIV2, respectively. Pneumatic branch lines 22, 24 pneumatically connect the bleed air supply lines 16a2 and 16b2 associated with the port and starboard bleed air subsystems 20.sub.PB, 20.sub.SB upstream of the ECS Pack 1 and ECS Pack 2 so as to deliver heated bleed air from Engine 1 and Engine 2 to the port and starboard piccolo tubes 30a, 30b, respectively. Activation of the WAIV1 and WAIV2 is accomplished by the controller 25 issuing a command signal when the anti-ice system 20 is to be operational. Such a command signal may be automatically generated in response to detection of ice by the aircraft sensors (not shown) and/or by manual activation by the pilot of the aircraft 10. Thus, in response to a command signal issuing from the controller 25, the WAIV1 and WAIV2 will open to supply heated air to the port and starboard piccolo tubes 30a, 30b via the port and starboard bleed air subsystems 20.sub.PB, 20.sub.SB, respectively.

[0022] The port and starboard anti-icing subsystems 20.sub.PS, 20ss may also include pressure and temperature sensors P1, T1 and P2, T2 so as to sense the pressure and temperature conditions of the heated bleed air being supplied to the piccolo tubes 30a, 30b via the port and starboard pneumatic bleed subsystems 20.sub.PB, 20.sub.SB, respectively. Each of the pressure and temperature sensors P1, T1 and P2, T2 is in operative communication with the controller 25 so the latter is provided with the pressure and temperature conditions of such heated bleed air being supplied to the piccolo tubes 30a, 30b. It is noted that the temperature sensors T1, T2 may be positioned in operative association anywhere in the port and starboard subsystems 20.sub.PB, 20.sub.SB downstream of the port side normally closed pressure regulating shut-off valve (PRSOV1) and the starboard side normally closed pressure regulating shut-off valve (PRSOV2), respectively.

[0023] The piccolo tube 30a is shown in FIG. 2 and is likewise representative of the piccolo tube 30b. As shown therein, the piccolo tube 30a includes a series of forwardly directed apertures 33 that allow the heated bleed air directed into the tube to impinge upon the interior surface of the leading edge 32a thereby heating the same and melting any accreted ice on the exterior surface of such leading edge 32a.

[0024] The controller 25 is also operatively connected by signal lines to the high pressure valves (HPV) identified as HPV1 and HPV2 associated with Engine 1 and Engine 2, as well as the operating valves identified as PRSOV1 and PRSOV2 operatively pneumatically associated with the bleed air supply lines 16a1 and 16b1, respectively. During normal operation therefore, bleed air will be supplied to the ECS Pack 1 and ECS Pack 2 via bleed air supply lines 16a1, 16a2 and 16b1, 16b2 via operation by the controller 25 of the HPV1, PRSOV1 and the HPV2, PRSOV2, respectively. Further during such normal operation, as noted above the WAIV1 and WAIV2 will allow a portion of the bleed air to be directed to the piccolo tubes 30a, 30b when commanded by the controller 25.

[0025] Important to the embodiment disclosed herein is the provision of an auxiliary power unit (APU) pneumatic bleed system 20.sub.APU which includes an on-board APU 40. As shown in FIG. 1, the APU 40 is provided with an APU bleed air supply line 40a that is pneumatically connected to each of the bleed air supply lines 16a1, 16a2 and 16b1, 16b2 through cross bleed valves (XBV) identified by XBV1 and XBV2 associated with the port and starboard pneumatic bleed air subsystems 20.sub.PB, 20.sub.SB, respectively. The APU bleed air supply line 40a includes an APU bleed valve (APUBV) which is connected operatively via a signal line to the controller 25. Actuation of the APUBV will therefore open the APUBV to allow bleed air from the APU to flow into the bleed air supply line 40a through an APU check valve (APUCKV) to the cross bleed valves XBV1 and XBV2. Each of the normally closed cross bleed valves XBV1 and XBV2 is independently operatively connected to the controller 25 via signal lines so as to be operated (opened) when needed to supply heated bleed air from the APU to either the bleed air supply line 16a2 or the bleed air supply line 16b2. The temperature of the heated bleed air supplied by the APU 40 may be sensed by a temperature sensor T3 in operative communication with the controller 25 that may operatively be associated with the supply line 40a at any position downstream of the APU 40 and upstream of the SBV1 and SBV2.

[0026] During an abnormal operation, e.g., one of Engine 1 or Engine 2 is incapable of delivering sufficient heated bleed air to the piccolo tubes 30a, 30b, respectively, the controller 25 may then issue a command signal to effectively allow heated bleed air to be supplied by the APU to the side of the aircraft having the abnormally operating Engine 1 or Engine 2 or an abnormally operating port and starboard anti-icing subsystems 20.sub.PS, 20ss, respectively. By way of example, should the port side Engine 1 fail or be compromised in any way so it cannot deliver sufficient bleed air, or should the port pneumatic bleed subsystem 20.sub.PS become nonoperational, the controller 25 may then issue respective command signals which close HPV1 and PRSOV1 and opens APUBV and XBV1. Such command signals will then allow heated bleed air from the APU to be delivered to the piccolo tube 30a on the port side of the aircraft 10 via the supply line 16a2 and the operation of WAIV1. A similar control scheme would be available should the starboard Engine 2 fail or be compromised in any way such that it cannot deliver sufficient bleed air or should the starboard pneumatic bleed subsystem 20ss become nonoperational, in which case the controller 25 would close the HPV2 and PRSOV2 and open the APUBV and the XBV2. Thus, by the term “single engine operational condition” is meant that only one of the port or starboard pneumatic bleed subsystems 20.sub.PS, 20ss, respectively, remains fully operational to supply heated engine bleed air to its respective airfoil while the other subsystem has failed and is incapable of supplying heated engine bleed air to its respective airfoil (e.g., due to a failure of one of the port or starboard engines (i.e., Engine 1 or Engine 2) or a failure of one of the port or starboard pneumatic bleed subsystems 20.sub.PS, 20ss, respectively).

[0027] As may be appreciated, during an abnormal anti-icing condition in response to a single engine operational condition (i.e., when one of the port or starboard engines Engine 1 or Engine 2, respectively, is not fully operational), the temperature of the bleed air delivered by the APU will have a different temperature as compared to the bleed air delivered by the engine that is operating normally. Thus, in order to maintain a balanced anti-icing system the wing anti-ice valves (WAIV1 or WAIV2) will be modulated by the controller 25 to maintain a heated bleed air supply of substantially equal energy to both the piccolo tubes 30a and 30b. Such a balanced energy system is achieved by programming the controller 25 with the mass flow curve for each of the piccolo tubes 30a and 30b. Since the mass flow curve is a function of pressure and temperature, by measuring the temperature of the bleed air being supplied to the wing anti-ice valve by the normally operating engine, the input pressure on the opposite side of the pneumatic anti-icing system 20 may then be modulated based on the measurement of the bleed air supplied by the APU using the equation:

[00002]${\text{EBA}}_{\text{T}}\times {\text{EBA}}_{\text{F}}={\text{APUBA}}_{\text{T}}\times {\text{APUBA}}_{\text{F}}$

where EBA.sub.T and EBA.sub.F are the temperature (K) and flow (kg/s), respectively, of the bleed air from the normally operating engine and APUBA.sub.T and APUBA.sub.F are the temperature and flow, respectively, of the bleed air from the APU.

[0028] Thus the sensed temperatures of the respective bleed air obtained by the sensors T1 and T2 associated with the port and starboard pneumatic bleed subsystems 20.sub.PS and 20ss, respectively, as well as the sensor T3 associated with the APU 40 are sent to the controller 25 via suitable signal connections therebetween. The controller 25 will also store in memory the mass flow curves for each of the piccolo tubes 30a and 30b. Thus, in the event of an engine failure, the controller 25 will calculate the necessary flow rates of the bleed air from the remaining normally operating engine and the APU 40 and will responsively modulate the wing anti-ice valves WAIV1 and WAIV2 to ensure energy balance is delivered to both the port side and the starboard side pneumatic bleed subsystems 20.sub.PS and 20ss, respectively.

[0029] While reference is made to a particular embodiment of the invention, various modifications within the skill of those in the art may be envisioned. Therefore, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope thereof.