GB2327358A

GB2327358A - Integrated aircrew garment system

Info

Publication number: GB2327358A
Application number: GB9715158A
Authority: GB
Inventors: Stuart John Mitchell
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1997-07-19
Filing date: 1997-07-19
Publication date: 1999-01-27
Also published as: GB9715158D0

Abstract

An integrated aircrew garment system comprising a breathing mask (2) connected to an oxygen supply (3) and a chest counter-pressure garment (8) connected to an air supply 6. The pressure supplied to the chest counter-pressure garment being controlled according to the pressure of oxygen supplied to the mask. The system will usually include anti G trousers also connected to said air supply. The pressure supplied to the chest counter-pressure garment can be regulated according to the pressure supplied to the mask, and/or to the anti G trousers depending on the altitude and G force experienced.

Description

Integrated aircrew garment system The invention relates to integrated garment systems comprising pressure garments of the type used by aircrew to counteract the effects of breathing oxygen at high pressure and of enduring high forces due to centrifugal forces in manoeuvring, hereinafter referred to as "G" forces.

Such garments include chest counter pressure garments and anti-G trousers.

Because of low ambient pressure at very high altitudes, it is necessary for aircrew when flying at altitude to breathe pressurised oxygen. This is normally provided to aircrew by means of breathing masks connected to a pressurised oxygen supply. During such pressure breathing at altitude, normal breathing action is altered; inhalation is passive wherein oxygen is forced under pressure into the lungs, and exhalation is active wherein aircrew have to forcibly exhale against the oxygen pressure. This is opposite to normal breathing action and can be very uncornfortable and distracting.

In order to alleviate this problem chest counter-pressure garments have been developed in the form of inflatable jackets to be worn around the aircrew's chest. Oxygen from a pressurised source is supplied to the pilot's mask and additionally supplied to the chest counter-pressure garment at a roughly equal pressure. Such a garment acts to exert pressure on the thorax externally so as to counteract the pressure from inside the lungs pushing outwards on the thorax due to the mask oxygen pressure. A conventional arrangement is for both the mask supply and the chest counter pressure garment supply to be connected to a common oxygen supply by a "Jerkin" connector. The Jerkin connector is essentially a T piece which connects the common oxygen supply to both chest counter pressure garment and mask. Commonly the pressure in the chest counter pressure garment is set to just below that of the mask pressure by the Jerkin connector by means of a valve located within the Jerkin connector and having a cracking pressure of 125 mm H20. This is a safety feature and ensures that any leak in the chest counter pressure garment does not prevent supply of oxygen to the mask. On lung inspiration, pressure in the chest counter pressure garment increases due to chest wall expansion. Because the chest counter pressure garment is rigidly fixed to the aircrew, a further dump valve, also located within the Jerkin connector, allows oxygen supplied to the chest counter-pressure garment to be vented to ambient during lung inhalation. A problem of such a system is that it wastes oxygen during pressure breathing. If there is no inlet valve, the system wastes oxygen all the time. A further problem also arises due to dynamic pressure changes occurring within the chest counter-pressure garment and mask hose as a result of the breathing cycle and also during rapid decompression. This causes a tendency of the valve diaphragms within the Jerkin connector to develop oscillations.

It is further known that when aircrew sustain high G forces (at any altitude), inflatable anti-O trousers similar in construction to the chest counter-pressure garment. These are inflated under pressure during high G manoeuvres so as to exert pressure on the legs so as to effectively "squeeze" them, preventing blood being drawn away from the upper part of the pilot's body.

An additional complication arises with the use of chest counter pressure garments in conjunction with inflatable anti-G trousers because both these garments have effects on the distribution of blood within the body portions (e.g. head, legs and chest).

It is known to provide pressurised oxygen to the mask and chest counter-pressure garment via a common supply wherein the pressure of oxygen supplied thereto is a function of the pressure of air supplied to anti-G trousers. Although this enables the pressure applied to the chest counter pressure garment to be regulated according to the pressure supplied to the anti -0 trousers, this only partially solves the problem of over- or under-pressure of blood to the head.

In this arrangement both mask and chest counter-pressure garment pressures are again approximately the same. Furthermore such a system is wasteful of oxygen because, as above during pressure breathing, on inhalation oxygen from the pressure garment is vented to ambient.

A further step in known systems is for the air pressure to the anti -0 trousers and the oxygen pressure to the chest counter pressure garment and mask to be controlled interdependently of each other. In such systems the pressure supplied to the anti-G trousers is dependent on not only the amount of G sustained but also on pressure of oxygen supplied to the mask/chest counter pressure garment as a result of altitude. Conversely the pressure supplied to the mask/chest counter pressure garment is, in addition to being dependent on altitude, dependent also on the pressure supplied to the anti -0 trousers as a result of G sustained. The operation of the chest counter pressure garment together with the anti -0 trousers ensures that the effects of the positive pressure breathing on blood distribution when operated at high altitudes are counteracted by inflation of the anti-G trousers. Although this further helps solve the problem of avoiding under/over pressure of blood to the head by giving greater flexibility in the control of pressure to the garments, the disadvantage of oxygen waste still remains. Moreover, having the mask and chest counter pressure garment at the same general pressure is not always ideal.

It is an object of this invention to provide an integrated garment system which unwasteful of oxygen and to provide pressure breathing under any G conditions which is comfortable and which adequately responds to the need to exert pressure on a pilot's chest, which in operation is smooth and controllable.

The invention consists of an integrated aircrew garment system for use in an aircraft comprising a breathing mask connected to an oxygen supply and further comprising a chest counter-pressure garment and anti-0 trousers both connected to a common supply of air.

The advantage of the invention is that it enables oxygen to be saved by using compressed air to supply the chest counter-pressure garment instead of oxygen.

The inventor has determined that in some instances it is preferable for the pressure of the mask to differ from the pressure of the chest counter-pressure garment and that if these pressures can be determined with more independence from each other, the flexibility of the garment system gives better control of blood distribution within the body and increased comfort of breathing.

Preferably the ratio of air pressure supplied to the chest-counter-pressure garment to oxygen pressure applied to the mask can be set to operate at one or more values or the ratio of air pressure supplied to anti-0 trousers to air pressure supplied to the chest-counter pressure garment can be set to operate at one or more values.

This allows the integrated garment system to be more flexible in providing an interdependant control of air/oxygen supply to each garment ensuring maximum aircrew comfort at any operating condition.

By way of example, the invention will now be described with reference to the drawings of which: Figure 1 shows a prior art aircrew garment system including anti-G trousers and breathing mask.

Figure 2 shows a prior art aircrew garment system which includes additionally a chest counter pressure garment.

Figure 3 shows a prior art aircrew garment system including a separate air supply for the anti G trousers.

Figure 4 shows an enhanced prior art aircrew garment system wherein the air supply to trousers and the oxygen pressure to the mask and chest counter pressure garment are mutually interdependent Figure 5 shows an embodiment of the invention comprising a mask and chest counter pressure garment each being supplied with its own oxygen and air supply respectively Figure 6 shows a further embodiment of the invention further including anti-0 trouser having a common air supply to the chest counter pressure garment.

Figure 7 shows a general schematic representation of the pressure control according to the invention.

Figure 1 shows a basic form of aircrew garment arrangement comprising a breathing system 1 comprising a breathing mask 2 connected to an oxygen supply 3 and controlled by a breathing gas regulator 4. The breathing gas regulator operates such that, because of high altitude, when ambient pressure drops below a certain pressure, oxygen is supplied to the pilot under pressure.

The breathing gas regulator therefore has an input from a pressure sensor. A typical pressure breathing for altitude schedule is shown in the table below: Altitude Pressure 38,000 ft 0mmHg 45,000ft 30mm Hg 50,000ft 45 mm Hg 55,000ft 60mmHg 60,000 ft 70 mm Hg Entirely separate anti-0 trousers 5 are connected to an air supply 6 via an anti-0 valve 7 which regulates pressure to the trousers according to the amount of G sustained; it has input from a G sensor. Such a system provides enhanced G protection to about 2 G and altitude protection to 50,000 feet. The major disadvantage of this system is that when breathing oxygen under pressure, there is a high pressure acting on the inside of the lungs and the pilot has to actively exhale against this pressure.

Figure 2 shows further a prior art aircrew garment system which includes like numbered components as described above and additionally includes an inflatable chest counterpressure garment 8. This acts to partially overcome the above mentioned pressure acting internally on the lungs and chest due to pressurised breathing by pushing externally on the pilot's chest. All three components, the mask, the chest counter pressure garment and anti-0 trousers are supplied by a common oxygen supply 3 which is controlled by breathing gas regulator which allows a pressurised oxygen supply to all the components. The chest counter-pressure garment 8 and breathing mask 2 are each connected to a Jerkin connector 9. The Jerkin connector essentially consists of a T connector whereby the oxygen supply divides into two conduits, one of which is provided with an chest counter pressure garment inlet valve such that the pressure supply to the chest counter pressure garment is slightly lower than that supplied to the mask.

This is for safety reasons and ensures that if the chest counter pressure garment develops a leak then there is still always a supply pressure of oxygen for breathing. A dump valve (not shown) is also included which allows oxygen to be released from the chest counter pressure garment on inhalation. The Jerkin connector is connected to a simple T piece 10 which is in turn connected to a oxygen supply via a breathing gas regulator 4 which regulates the mask, chest counter pressure garment and anti-G trouser pressure to be dependant on altitude. In this arrangement the chest counter pressure garment and G trousers are only activated if the cabin pressurisation has failed and the cabin altitude raised above a set level typically around 38,000 ft. The anti-0 trousers are incorporated so as to prevent blood being squeezed to the lower part of the body by inflation of the chest by pressure breathing; they are not arranged to be activated according to G sustained. Thus no enhanced G protection is provided and further, the system is wasteful of oxygen during pressure breathing.

Figure 3 shows an improved conventional aircrew garment arrangement comprising a chest counter-pressure garment and breathing mask each connected to a Jerkin connector as in common with the system described above. In this arrangement the anti-G trousers are supplied from a separate air supply 6 via an anti-G valve 12, configured such that the air pressure applied to the trousers is dependant on the amount of G sustained by the aircraft. Additionally the pressure of oxygen supplied to the Jerkin connector (and hence mask and chest counter pressure garment) is regulated by a breathing regulator to be dependent on altitude. A pneumatic signal 13 from the anti-0 trousers (which determines G-trouser pressure) to the breathing gas regulator allows oxygen pressure to the Jerkin connector to be additionally dependant on the air pressure supplied to the anti-0 trouser according to a set schedule. For altitude protection the breathing regulator senses ambient pressure and delivers the appropriate breathing and anti-0 trouser pressure. A typical pressure breathing for G schedule is shown below.

G schedule G trouser pressure Breathing/chest counter pressure garment pressure Cut in at 2G = 78 rnm Hg Cut in at 2G = O mm Hg Slope=65mmHg/G Slope= 12mmHg/G Plateau at 9 G = 530 mm Hg Plateau at 8G = 65 mm HIG The system allows the mask and chest counter pressure garment to be pressurised when the pulling G thus allowing both the anti-0 trousers and chest counter pressure garment to operate to prevent blood being drawn from the head. However, at altitude when no G is sustained, the trousers do not operate. This means that there is often too much pressure applied to the chest and results in over-pressure to the lower part of the torso. A further problem is that when sustaining G the pilot is forced to breathe oxygen under pressure unnecessarily which is uncomfortable because of the altered breathing mode.

Figure 4 shows an alternative prior art system which comprises generally the same components having corresponding reference numerals as described above. Compressed air which is supplied to the anti-0 trousers is controlled by an anti-0 valve as before, but it is made dependent on the pressure of oxygen supplied to the mask and chest counter pressure garment by means of a pneumatic signal 14 from the breathing regulator. As before, by means of a pneumatic signal 13, the oxygen pressure supplied to the Jerkin connector is regulated to be dependent on the pressure supplied to the anti-G trousers as well as the altitude.

In this arrangement, when no G is sustained, at altitude the trousers will nethertheless be pressurised to overcome the effects of pressure breathing and squeezing the chest by the chest counter pressure garment. Any suitable schedule regime for how G trouser pressure is regulated according to the chest counter pressure garment /mask pressure can be utilised.

Likewise when G is sustained the chest counterpressure garment is partially pressurised which further assists in preventing blood from being drawn from the head. Any suitable schedule of how the mask/chest counter pressure garment pressure is dependent on G can be used such as the one described above.

In these systems when both high altitude and high G are sustained, the pressure supply to the anti G trousers is not additive according to the schedules. The pressure supply is determined as follows: if the pressure to the trousers as determined by the G schedule is higher than the pressure according to the altitude schedule, then it is the G schedule which is applied; otherwise it is the pressure as determined by the altitude schedule. Similarly when high altitude and G conditions are extant, the mask/chest counter pressure garment pressure is determined as follows; if the pressure as determined by the altitude schedule is greater that that determined by the G schedule then it is the former pressure which is applied, otherwise it is the pressure to the mask/chest counter pressure garment as determined by the G schedule. For example when pulling 5G at 50,000 ft according to the above altitude schedule, a pressure of 45 mm Hg should be supplied to the mask/chest counter pressure garment. According to the G schedule above, a pressure of (5-2) x 12 = 36 mm Hg should be applied to the mask/chest counterpressure garment. It is therefore the higher of these two pressures, 45 mm Hg which is applied to the mask/chest counter-pressure garment.

Alternatively the control may be as set according to ratios; e.g. the pressure applied to the anti G trousers may be set at say twice the applied breathing pressure. This ratio may be varied according to G sustained; e.g. 12:1 at 3 G to 8:1 at 9G but is fixed at say 2:1 for altitude protection.

In all the above prior art systems the mask and chest counter pressure garment pressure are set at roughly the same pressure. As a safety feature the mask pressure is always somewhat above the chest counter pressure garment pressure. Therefore although the chest counter pressure garment reduces the problem of forced inhalation and active exhalation it is not completely eliminated. Additionally all of the above systems waste oxygen to a greater or lesser degree.

Figure 5 shows a basic embodiment of the invention. The system comprises a breathing mask 2 connected via a breathing regulator 4 to an oxygen supply 3 and a chest counter pressure garment connected to a separate air supply via a chest counter pressure garment pressure controller 15. A pneumatic signal 16 from the mask supply to the CCPG pressure controller regulates the pressure to the chest counter pressure garment dependent on mask pressure. The oxygen pressure to the mask is set according to known regimes as described above. The pressure of gas supplied to the chest counter pressure garment is regulated to be a function of the mask pressure. Preferably the chest counter pressure garment is set to a small amount above the mask pressure which overcomes the problems of forced inhalation and active exhalation. In all prior art arrangements the mask pressure is set higher than the chest counter pressure garment pressure in case of chest counter pressure garment leakage. However this problem does not arise with the invention because the breathing mask has its own oxygen supply, separate from that of the chest counter pressure garment. The system eliminates wastage of oxygen by the chest-counter pressure garment and also enables CCPG pressure to be controlled independently to the mask pressure.

Figure 6 shows an aircrew garment system according to a further embodiment of the invention.

In this arrangement, the system comprises a mask, a chest counter-pressure garment and anti-0 trousers as before. The anti-0 trousers and the chest counter pressure garment are both connected to a common air supply 6; the anti-G trousers via an anti-0 valve 7 and the chest counter pressure garment via a chest counter pressure garment pressure controller 15. The chest counter pressure garment pressure controller controls the supply pressure of air to the counter pressure garment so as to be dependent on the air pressure supplied to the anti-G trousers and oxygen pressure to the mask by means of pneumatic signals 16 and 17 from downstream of the anti-G valve and from the oxygen pressure regulator respectively. The chest counter pressure garment pressure controller additionally comprises a rapid decompression aneroid/maximum pressure relief valve (not shown) which allows venting of the chest counter pressure garment should rapid decompression occur. As in the previous example, the chest counter-pressure garment is supplied with compressed air, from a supply common with the anti-G trousers, rather than oxygen. Pressure to the anti-0 trousers is dependent on the G sustained by means of the anti-0 valve and also on the pressure supplied to the mask by means of a pneumatic signal 18. Likewise, pressure supplied to the mask is dependent on altitude by means of the breathing gas regulator but also on the anti-G trouser pressure by means of pneumatic signal.

Figure 7 shows a schematic representation of the components within the dotted line of figure 6, which can be effectively be viewed as an overall ratio controller.

The overall ratio controller can be set so that air supply pressure to the chest counter pressure garment is a ratio of mask pressure and/or anti-0 trouser pressure and this ratio may be varied according to a pre-set regime according to the amount of G sustained and the altitude. For example, a range of mask:chest counter-pressure garment ratios can be operated depending on the altitude and the amount of G sustained, and which can be set in advance.

Preferred ratios of the chest counter pressure garment to mask oxygen pressure are shown in the table below, and these ratios are made dependent on two modes of operation; whether pressure breathing for altitude or pressure breathing under G force. This will depend on the altitude and/or G sustained.

Table 1: Chest counter-pressure garment pressure to mask pressure for various configurations.

Example configurations Pressure breathing for altitude Pressure breathing for gravity 1 1:1 1:1 2 1:1 0.75:1 3 1.5:1 0.75:1 4 1.5:1 1:1 Although the invention has been described by means of the above examples, the invention embodies a wide range of configurations wherein the supply pressure of oxygen to the breathing mask, air pressure to the chest counter-pressure garment, and air to the anti-0 trousers are all dependant on the altitude and G sustained. Figure 8 shows a generalised scheme of the invention comprising two supply conduits, one supplying pressurised oxygen, the other supplying pressurised air, both input to a overall controller. Signals from a pressure sensor and an altitude sensor are also applied to the controller. Three output conduits from the controller supply the mask with oxygen, the chest counter pressure garment with either oxygen or air, and the G trousers with air. Essentially the controller acts to provide pressure to all three components as functions of G sustained and ambient pressure.

Claims

1. An integrated aircrew garment system comprising a breathing mask connected to an oxygen supply and a chest counter-pressure garment connected to an air supply and means for controlling the pressure supplied to the chest counter-pressure garment according to the pressure of oxygen supplied to the mask.

2. An integrated garment as claimed in claim 1 pressure supplied to the chest-counter pressure garment is set at a fixed pressure differential above that of the oxygen supply pressure to the mask.

3. An integrated aircrew garment system as claimed in claims 1 or 2 additionally comprising anti G trousers also connected to said air supply.

4. An integrated aircrew garment system as claimed in claims 3 wherein the ratio of air pressure supplied to anti-G trousers to air pressure supplied to the chest-counter pressure garment can be set to operate at values being dependent on the amount of G and the altitude sustained by the aircrew.

5. An integrated aircrew garment system as claimed in claims 3 or 4 wherein when a preset altitude is attained, the ratio of chest counter pressure garment air supply pressure to mask oxygen supply pressure is between 0.5:1 and 2:1.

6. An integrated aircrew garment system as claimed in claims 3 or 4, wherein when a preset amount of G is sustained by the aircraft, the ratio of chest counter-pressure garment air supply pressure to mask oxygen supply pressure is between 0.5:1 to 2:1.

7. An integrated aircrew garment system substantially as hereinbefore described with reference to the drawings.