WO2009036808A1

WO2009036808A1 - Timepiece with true airspeed indicator

Info

Publication number: WO2009036808A1
Application number: PCT/EP2007/060024
Authority: WO
Inventors: Yeslam Binladin
Original assignee: Senses Ltd.
Priority date: 2007-09-21
Filing date: 2007-09-21
Publication date: 2009-03-26
Also published as: CH697906A2; WO2009037189A1

Abstract

The invention concerns a timepiece (1) with an integrated true airspeed indicator, which comprises a case that is closed by a glass (5) and formed of a back cover (2) and a middle part (3); a time display (6); a bezel (7) comprising a rotatable part (8) with a circular first edge (9); a time keeping circuit (10) controlling the time display (6); and at least one energy source (11) powering the time-keeping circuit (10). One preferred embodiment of the timepiece according to the invention is characterized in that the bezel (7) comprises Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks that are in each case directed radial to the first edge (9) of the rotatable part (8) of the bezel (7) and that are diametrically opposed to each other. The inventive timepiece (1) comprises an indicator ring (12) with a circular first edge (13) that is concentrically arranged with and that is located close to the first edge (9) of the rotatable part (8) of the bezel (7). The fixed indicator ring (12) comprises Flight Level (F. L.) marks and Knots True Air Speed (K. T. A. S.) marks that are in each case directed radial to the first edge ( 13) of the indicator ring (12) and that are diametrically opposed to each other in such a way that the (K. I. A. S.) marks of the rotatable part (8) of the bezel (7) are located opposite the (F. L.) marks of the indicator ring (12) and that the (F. L.) marks of the rotatable part (8) of the bezel (7) are located opposite the (K. T. A. S.) marks of the indicator ring (12). Also disclosed are uses of the inventive timepiece for estimating the true airspeed of an aircraft.

Description

Timepiece with true airspeed indicator

The present invention relates to a timepiece with true airspeed indicator. The timepiece comprises: a case formed of a back cover and a middle part, the case being closed by a glass; a time display; a bezel mounted on the middle part and surrounding the time display, the bezel comprising a rotatable part with a circular first edge; a time keeping circuit disposed in the case and controlling the time display; and at least one energy source powering the timekeeping circuit. The invention more particularly concerns a wristwatch or pocket watch enabling a user, particularly a pilot, to estimate the true airspeed with respect to an aircraft on ground or in the air.

There are many factors in aviation that a pilot has to take into consideration. One particular item of special interest the present invention is concerned with is "True Airspeed" or T. A. S.. As educated pilots know, the input for a standard airspeed indicator is both ram air pressure and static air pressure. The instrument in the cockpit shows the difference between ram air pressure and static air pressure, which difference then is translated into "Indicated Airspeed" or I. A. S.. Thus, an airspeed indicator is a differential pressure gauge with the pressure reading expressed in units of speed, rather than pressure. The airspeed is derived from the difference between the ram air pressure from the pitot tube(s) and static pressure. The static pressure is frequently detected at static ports on one or both sides of the aircraft. However, indicated airspeed (LA. S.) is the airspeed indicator reading uncorrected for instrument position, and other errors. Indicated airspeed means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for air- speed system errors. Hence there is no correction for (air)temperature, or (air)pressure.

The true airspeed (T. A. S) is the speed of an aircraft relative to the air mass in which it flies, i.e. the magnitude of the vector difference of the velocity of the air- craft and the velocity of the air. Under zero wind conditions and in horizontal flight, this is equal to the speed over the ground. Under wind conditions, an estimation of the wind is used to make a wind speed vector calculation that computes an estimated ground speed from the true air speed and a wind correction angle to maintain the desired ground track.

Indicated airspeed (I. A. S) will differ from true airspeed at air densities other than some reference density. Air density is affected by temperature, moisture content, and altitude. Indicated airspeed is used in aircraft operations as the aircraft's stall speed and structure limit speed, irrespective of true airspeed. However, proper navigation via dead reckoning (without constant ground reference) requires the use of true airspeed and wind corrections, if necessary.

When an aircraft climbs, a decrease in both the air temperature (-2 ⁰C per 1000 feet or about 300 meters) as well as the air pressure (37 mbar per 1000 feet or about 300 meters) is experienced. For reference purposes, the length of a foot is approximated by 0.3 m. In the following, it is referred to the conditions of the International Standard Atmosphere (ISA) as it is widely known and accepted. The ISA is an atmospheric model of how the pressure, temperature, density, and viscosity of the earth's atmosphere change over a wide range of altitudes. The ISA consists of tables of values at various altitudes, plus some formulas by which those values were derived. The International Organization for Standardization (ISO) publishes the ISA as an international standard ISO 2533: 1975. Other standards organizations, such as the International Civil Aviation Organization (ICAO)

S44 0001 P WO2 doc and the United States Government, publish extensions or subsets of the same atmospheric model under their own standards-making authority. The (ICAO) published their "ICAO Standard Atmosphere" as Doc 7488-CD in 1993. It has the same model as the ISA, but extends the altitude coverage to 80 kilometers (262,500 feet).

The ISA model divides the atmosphere into layers with linear temperature distributions. The other values are computed from basic physical constants and relationships. Thus the standard consists of a table of values at various altitudes. For example, at sea level the standard gives a pressure of 1.013 bar and a temperature of 15°C, and an initial lapse rate of -6.5 °C/km. Above 12 km, the tabulated temperature is essentially constant. The tabulation continues to 18 km where the pressure has fallen to 0.075 bar and the temperature to -56.5 ⁰C. The ISA model is based on average conditions at mid latitudes, as determined by ISO's TC 20/SC 6 technical committee. It has been revised from time to time since the middle of the 20th century.

S44 0001 P WO2 doc This ISA model of course has a significant influence on the indication of an airspeed instrument. Therefore, with an increase in altitude (better, decrease of temperature and/or pressure), the instrument error will increase. As a consequence, the difference between indicated airspeed and true airspeed will become greater.

As said, the indicated airspeed is very important for airplane matters, such as stall speed and structural limit. However, on a normal flight with the preflight preparation done, one can stay well clear of both. Thus, every pilot is interested in the true airspeed.

During routine flight preparation, the pilot in command of the oncoming flight is responsible for an accurate but estimated/expected true airspeed, because these data are required for the flight plan. In the case that the actual true airspeed dif- fers more than 10 knots (+ or -), the Air Traffic Control has to be informed. Normally, one would find the true airspeed by taking the indicated airspeed, cruise level and temperature (at cruising level) into a graph in the Aircraft Flight Manual.

The importance of true airspeed is best understood during the flight planning stage of a flight. Where the indicated airspeed is very important for matters such as stall speed and structural limit, it is the true airspeed that is needed for use for flight time and distance calculations. Keeping in mind that this is air distance. Of course if a pilot wishes to know how long it will take to fly from one point to the next, over the ground, he must add the track wind component (TWC) to the equation.

K. T. A. S. is true airspeed given in knots (knots = nautical mile per hour, 1 nautical mile « 1852 meters). All cross country aviation calculations are based on fly- ing at the planned true airspeed, generally defined as the speed of the airplane through the relatively undisturbed air mass. K. I. A. S. is indicated airspeed given in knots.

S44-0001P-WO2 doc From the prior art, there are many methods known for calculation of the true airspeed in a simple aircraft without an air data computer or mach meter. The true airspeed can be calculated as a function of the local air density (or static air temperature and pressure altitude which determine density). Some airspeed indica- tors incorporate a slide rule mechanism to perform this calculation. Otherwise, estimation of true airspeed can be performed with a calculator such as the E6B "whiz wheel" or "asa E6-B FLIGHT COMPUTER" handheld circular slide rule.

It is the objective of the present invention to provide a timepiece with true air- speed indicator.

This objective is achieved according to a first aspect, by a timepiece as previously described and according to the features of the independent claim 1. The timepiece according to the invention is characterized in that the bezel comprises Indi- cated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks that are in each case directed radial to the first edge of the rotatable part of the bezel and that are diametrically opposed to each other. The timepiece comprises an indicator ring with a circular first edge that is concentrically arranged and that is located close to the first edge of the rotatable part of the bezel. The indicator ring is fixed to the middle part of the timepiece and comprises Flight Level (F. L.) marks and Knots True Air Speed (K.T.A.S.) marks that are in each case directed radial to the first edge of the indicator ring and that are diametrically opposed to each other in such a way that the (K. I. A. S.) marks of the rotatable part of the bezel are located opposite the (F. L.) marks of the indicator ring and that the (F. L.) marks of the rotatable part of the bezel are located opposite the (K.T.A.S.) marks of the indicator ring.

This objective is achieved according to a second aspect, by a timepiece as previously described and according to the features of the independent claim 4. The timepiece according to the invention is characterized in that the bezel comprises Flight Level (F. L.) marks and Knots True Air Speed (K.T.A.S.) marks that are in each case directed radial to the first edge of the rotatable part of the bezel and that are diametrically opposed to each other. The timepiece comprises an indica-

S44-0001P-WO2 doc tor ring with a circular first edge that is concentrically arranged and that is located close to the first edge of the rotatable part of the bezel. The indicator ring is fixed to the middle part of the timepiece and comprises Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks that are in each case directed ra- dial to the first edge of the indicator ring and that are diametrically opposed to each other in such a way that the (F. L.) marks of the rotatable part of the bezel are located opposite the (I. A. S.) marks of the indicator ring and that the (KT. A. S.) marks of the rotatable part of the bezel are located opposite the (F. L.) marks of the indicator ring.

Additional preferred and inventive elements and features derive from the dependent claims in each case. Also disclosed are uses of the inventive timepiece for estimating the true airspeed of an airborne aircraft that is equipped with an altimeter and an airspeed indicator and for estimating the expected true airspeed of an aircraft, when on the ground.

The timepiece of the invention is now described in greater detail on the basis of exemplary embodiments and with the help of accompanying schematic drawings that illustrate a preferred embodiment of the present invention and that are not intended to limit the scope of the invention. It is shown in :

Fig. 1 a plain view of a timepiece with an analogue time display and an integrated true air speed indicator according to a first embodiment of the arrangement of the bezel and the indicator ring;

Fig. 2 a cross section through a timepiece with a first and second variant to the first embodiment of the arrangement of the bezel and the indicator ring as shown in Fig. 1.

Figure 1 shows a plain view of a timepiece 1 with an analogue time display and an integrated true air speed indicator according to a first embodiment of the arrangement of the bezel 7 and the indicator ring 12. The timepiece 1 comprises a case formed of a back cover 2 and a middle part 3, the case being closed by a

S44-0001 P-WO2 doc glass 5 (see Fig. 2). The timepiece further comprises a time display 6; a bezel 7 mounted on the middle part 3 and surrounding the time display 6. The bezel 7 comprises a rotatable part 8 with a circular first edge 9. The timepiece also comprises a time keeping circuit 10 disposed in the case and controlling the time dis- play 6 and at least one energy source 11 powering the timekeeping circuit 10 (see Fig. 2).

The bezel 7 of the timepiece 1 of the present invention - according to the first embodiment - comprises Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks that are in each case directed radial to the first edge 9 of the rotatable part 8 of the bezel 7 and that are diametrically opposed to each other. The inventive timepiece 1 comprises an indicator ring 12 with a circular first edge 13 that is concentrically arranged with and that is located close to the first edge 9 of the rotatable part 8 of the bezel 7. The indicator ring 12 is fixed to the middle part 3 of the timepiece 1 and comprises Flight Level (F. L.) marks and True Air Speed (K.T.A.S.) marks that are in each case directed radial to the first edge 13 of the indicator ring 12 and that are diametrically opposed to each other in such a way that the (K. I. A. S.) marks of the rotatable part 8 of the bezel 7 are located opposite the (F. L.) marks of the indicator ring 12 and that the (F. L.) marks of the rotatable part 8 of the bezel 7 are located opposite the (K.T.A.S.) marks of the indicator ring 12.

The timepiece 1 preferably comprises an analogue time display 6 with 12 hour positions and with an hour hand 14 and a minute hand 15, and a crown 4 at the three o'clock position. On this exemplary timepiece 1, the (K. I. A. S.) marks of the rotatable part 8 of the bezel 7 and the opposed (F. L.) marks of the indicator ring 12 are located on a top side 18 of the timepiece 1, preferably between the 10 o'clock and 2 o'clock positions. The (F.L.) marks of the rotatable part 8 of the bezel 7 and the opposed (K.T.A.S.) marks of the indicator ring 12 of this exem- plary timepiece 1 are located on a bottom side 19 of the timepiece 1, preferably between the 4 o'clock and 8 o'clock positions.

S44 0001 P W02 d0( Alternatively (not shown), the timepiece 1 comprises a digital time display 6. The (K. I. A. S.) marks of the rotatable part 8 of the bezel 7 and the opposed (F. L.) marks of the indicator ring 12 of this alternative variant preferably are located on a top side 18 of the timepiece 1, wherein the (F. L.) marks of the rotatable part 8 of the bezel 7 and the opposed (K. T. A. S.) marks of the indicator ring 12 preferably are located on a bottom side 19 of the timepiece 1 with a digital time display.

According to a second embodiment of the arrangement of the bezel 7 and the indicator ring 12 (not shown), the timepiece 1 comprises the same basic elements, a case that is closed by a glass 5 and formed of a back cover 2 and a middle part 3; a time display 6; a bezel 7 comprising a rotatable part 8 with a circular first edge 9; a time keeping circuit 10 disposed in the case and controlling the time display 6; and at least one energy source 11 powering the timekeeping circuit 10 (see Fig. 2).

The bezel 7 of the timepiece 1 of the present invention - according to the second embodiment - comprises Flight Level (F. L.) marks and True Air Speed (K. T. A. S.) marks that are in each case directed radial to the first edge 9 of the rotatable part 8 of the bezel 7 and that are diametrically opposed to each other. The inven- tive timepiece 1 comprises an indicator ring 12 with a circular first edge 13 that is concentrically arranged with and that is located close to the first edge 9 of the rotatable part 8 of the bezel 7. The indicator ring 12 is fixed to the middle part 3 of the timepiece 1 and comprises Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks that are in each case directed radial to the first edge 13 of the indicator ring 12 and that are diametrically opposed to each other in such a way that the (F. L.) marks of the rotatable part 8 of the bezel 7 are located opposite the (K. I. A. S.) marks of the indicator ring 12 and that the (K.T.A.S.) marks of the rotatable part 8 of the bezel 7 are located opposite the (F. L.) marks of the indicator ring 12.

The timepiece 1 preferably comprises an analogue time display 6 with 12 hour positions and with an hour hand 14 and a minute hand 15, and a crown 4 at the three o'clock position. On this exemplary timepiece 1, the (F. L.) marks of the ro-

S44-0001P-WO2 doc tatable part 8 of the bezel 7 and the opposed (K. I. A. S.) marks of the indicator ring 12 are located on a top side 18 of the timepiece 1, preferably between the 10 o'clock and 2 o'clock positions wherein the (K. T. A. S.) marks of the rotatable part 8 of the bezel 7 and the opposed (F. L.) marks of the indicator ring 12 are lo- cated on a bottom side 19 of the timepiece 1, preferably between the 4 o'clock and 8 o'clock positions.

Alternatively (not shown), the timepiece 1 comprises a digital time display 6 and the (F. L.) marks of the rotatable part 8 of the bezel 7 and the opposed (K. I. A. S.) marks of the indicator ring 12 are located on a top side 18 of the timepiece 1, wherein the (K. T. A. S.) marks of the rotatable part 8 of the bezel 7 and the opposed (F. L.) marks of the indicator ring 12 are located on a bottom side 19 of the timepiece 1.

Figure 2 shows a cross section through a timepiece 1 with a first and second variant to the first embodiment of the arrangement of the bezel 7 and the indicator ring 12 as shown in Fig. 1. All basic and all inventive elements of a timepiece 1 are shown here: The case is closed by a glass 5 and formed of a back cover 2 and a middle part 3. There is a time display 6 and a bezel 7 comprising a ro- tatable part 8 with a circular first edge 9. A time keeping circuit 10 is disposed in the case and controlling the time display 6. Also disposed in the case is at least one energy source 11 that powers the timekeeping circuit 10.

In this Figure 2, there are two alternative variants of the arrangement of the bezel 7 and the indicator ring 12 disclosed. On the left, the indicator ring 12 visually is a part of the bezel 7 of the timepiece 1 and located above the glass 5. However, also in this case, the indicator ring 12 is fixed and cannot be rotated. Thus, only the rotatable part 8 of the bezel 7 can be rotated with respect to the indicator ring 12. This variant according to the left side in Figure 2 has the ad- vantage that the two circular edges 9,13 of the rotatable bezel part 8 and of the indicator ring 12 are in very close proximity. This enables precise alignment of the scales of the rotatable bezel part 8 and of the indicator ring 12 and readout of the True Air Speed (K.T.A.S.) value without optical parallax error.

S44 0001P WO2 doc On the right, the indicator ring 12 is a part of the middle part 3 and located below the glass 5. As it is obvious in this case, the indicator ring 12 is fixed and cannot be rotated and only the rotatable part 8 of the bezel 7 can be rotated with respect to the indicator ring 12. This variant according to the right side in Figure 2 has the advantage that the area of the rotatable bezel part 8 and of the indicator ring 12 in each case can be larger. This allows larger and better readable scales and letters to be applied to the rotatable bezel part 8 and to the indicator ring 12 and, thus, easier readout of the True Air Speed (K. T. A. S.) value.

It is preferred that the rotatable part 8 of the bezel 7 of the timepiece 1 according to the invention comprises a surface that presents a surface with enhanced grip. This surface can be corrugated or corded, however a rubber application 16 attached to at least a part of the circumference 17 of the rotatable part 8 of the bezel 7 is preferred. Also combinations of corded surface and pieces of rubber applications are conceivable. Especially preferred is a ring-like rubber application 16 around the circumference 17 of the rotatable bezel part 8 as shown in Fig. 1.

The time keeping circuit 10 or movement of the timepiece 1 can be mechanical or electronic. Mechanical movements are well known as "tourbillon" or as "auto- matic" clockworks. A tourbillon is a type of mechanical clock or watch escapement invented in 1795 by Abraham-Louis Breguet that is designed to counter the effects of gravity and other perturbing forces that can affect the accuracy of a chronometer. In a tourbillon, the entire escapement assembly rotates, including balance wheel, escapement wheel, and pallet fork. The rate of rotation varies per design but has generally become standardized at one rotation per minute. Thus, the energy source 11 in tourbillon is the entire escapement assembly. There are many "Tourbillon" fake/replicas of premium brand watches that emulate this feature with the oscillating balance wheel visible through the watch dial. However, these are usually conventional lever escapements of automatic clockworks, not tourbillons. Electronic movements are well known as "quartz" clockworks. A quartz clock is a clock that uses an electronic oscillator that is made of a quartz crystal to keep precise time. This crystal oscillator creates a signal with very precise frequency. Generally, a time keeping circuit 10 in some form of digital logic

S44 0001 P WO2 doc counts the cycles of this signal and provides a numeric time display. The energy source 11 in a quartz timepiece usually is an electrical source implemented as a battery or an accumulator.

Irrespective of the type of the time keeping circuit 10 or movement and of the energy source 11 of the timepiece 1, the bezel 7 with its Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks and the indicator ring 12 with its Flight Level (F. L.) marks and True Air Speed (K. T. A. S.) marks (according to the first embodiment of the invention) are usable for the estimation of the true air- speed in a simple aircraft without an air data computer or mach meter. The same is true for the or second embodiment of the invention, in which the scales with the Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks as well as with the Flight Level (F.L.) marks and True Air Speed (K.T.A.S.) marks are interchanged on the bezel 7 and on the indicator ring 12. However, one especially preferred embodiment of the timepiece 1 according to the invention is based on an automatic movement (time keeping circuit 10) and incorporates an analogue time display 6 with an hour hand 14 and minute hand 15.

The timepiece 1 preferably is embodied as a wristwatch or as a pocket watch. Especially preferred is the embodiment of the inventive timepiece 1 as a wrist- watch.

The use of the timepiece 1 according to the invention for estimating the true airspeed is now explained on the base of the first embodiment of the invention as shown in the figures 1 and 2:

When on the ground ;

The requested Flight Level (F.L.) value and the anticipated Indicated Air Speed (K. I. A. S.) value are lined up on a top side 18 of the timepiece 1. Preferably, the requested Flight Level (F.L.) value is on the inner scale, i.e., on the indicator ring 12, and the anticipated Indicated Air Speed (K. I. A. S.) in knots is on the outer scale, i.e., on the rotatable part 8 of the bezel 7. As an example, a requested

S44 0001 P-WO2 doc Flight Level (F. L.) value of 300 feet and the anticipated Indicated Air Speed (K. I. A. S.) of 318 knots are indicated with a bold arrow in Fig. 1.

Than the corresponding requested Flight Level (F. L.) is found on a bottom side 19 of the timepiece 1. Preferably, the requested Flight Level (F. L.) value is on the outer scale, i.e., on the rotatable part 8 of the bezel 7 (see solid arrow in Fig. 1). Now, opposite the corresponding Flight Level (F. L.) on the bottom side 19 of the timepiece 1, preferably on the inner scale (the indicator ring 12), the True Air Speed in knots (K. T. A. S.) is estimated. According to this example, the true air- speed is estimated to be about 510 knots.

When airborne, on the flight deck of an aircraft that is equipped with an altimeter and an airspeed indicator:

The actual, current Flight Level (F. L.) is read from the altimeter of the aircraft that previously has been set to standard setting (1013 hPa or 29,92" mercury) and the Indicated Air Speed (K. I. A. S.) on the airspeed indicator of the aircraft is read in knots. The actual (F. L.) and (K. I. A. S.) values are preferably aligned on a top side 18 of the timepiece 1. Preferably, the current Flight Level (F. L.) value is on the inner scale, i.e., on the indicator ring 12, and the current Indicated Air Speed (K. I. A. S.) in knots is on the outer scale, i.e., on the rotatable part 8 of the bezel 7.

Than, the corresponding Flight Level (F. L.) is found on a bottom side 19 of the timepiece 1, preferably on the outer scale, i.e., on the rotatable part 8 of the bezel 7. Now, opposite the corresponding Flight Level (F. L.) on the bottom side 19 of the timepiece 1, preferably on the inner scale (the indicator ring 12), the True Air Speed in knots (K. T. A. S.) is estimated.

Whereas the scales on the timepiece of the invention are based on the ISA condi- tions, they can practically arbitrary chosen in a wide range as follows; The Flight Level (F. L.) is indicated between 80 and 800 feet. The Indicated Air Speed (K. I. A. S.) is indicated between 100 knots and 500 knots. The True Air Speed in Knots (K. T. A. S.) is indicated between 200 and 900 knots.

S44-0001 P-WO2 doc The particularly preferred scales on the timepiece of the invention are based on the ISA conditions as follows:

The Flight Level (F.L.) is indicated between 180 and 460 feet. The Indicated Air Speed (K. I. A. S.) is indicated between 190 knots and 360 knots. The True Air Speed in Knots (K. T. A. S.) is indicated between 350 and 650 knots.

Any combinations of the features of the individual embodiments disclosed herein belong to the scope of the present invention. The same reference numbers are given to the same features shown in the drawings, even when they are not spe- cifically addressed in the specification in each case.

List of reference numerals:

1 timepiece, wrist watch, pocket watch

2 back cover

3 middle part

4 crown

5 glass

6 time display

7 bezel

8 rotatable part of 7

9 circular first edge of 8

10 time keeping circuit

11 energy source

12 indicator ring

13 first edge of 12

14 hour hand

15 minute hand

16 rubber application

17 circumference of 8

18 top side of 1

19 bottom side of 1

S44-0001P-WO2 doc

Claims

Patent Claims

1. A timepiece ( 1) comprising :

- a case formed of a back cover (2) and a middle part (3), the case being closed by a glass (5); a time display (6); a bezel (7) mounted on the middle part (3) and surrounding the time display (6), the bezel (7) comprising a rotatable part (8) with a circular first edge (9); - a time keeping circuit (10) disposed in the case and controlling the time display (6); and at least one energy source (11) powering the timekeeping circuit (10); characterized in that the bezel (7) comprises Indicated Air Speed (K. I. A. S.) marks and Flight Level (F. L.) marks that are in each case directed radial to the first edge (9) of the rotatable part (8) of the bezel (7) and that are diametrically opposed to each other, wherein the timepiece (1) comprises an indicator ring (12) with a circular first edge (13) that is concentrically arranged with and that is located close to the first edge (9) of the rotatable part (8) of the bezel (7), the indicator ring (12) being fixed to the middle part (3) of the timepiece (1) and comprising Flight Level (F. L.) marks and True Air Speed (K. T. A. S.) marks that are in each case directed radial to the first edge (13) of the indicator ring ( 12) and that are diametrically opposed to each other in such a way that the (K. I. A. S.) marks of the rotatable part (8) of the bezel (7) are located opposite the (F. L.) marks of the indica- tor ring ( 12) and that the (F.L.) marks of the rotatable part (8) of the bezel

(7) are located opposite the (K. T. A. S.) marks of the indicator ring ( 12).

2. The timepiece of claim 1, comprising an analogue time display (6) with 12 hour positions and with an hour hand (14) and a minute hand (15), and a crown (4) at the three o'clock position, characterized in that the

(K. I. A. S.) marks of the rotatable part (8) of the bezel (7) and the opposed (F.L.) marks of the indicator ring (12) are located on a top side (18) of the timepiece (1), preferably between the 10 o'clock and 2 o'clock positions,

S44 0001 P WO2 doc wherein the (F. L.) marks of the rotatable part (8) of the bezel (7) and the opposed (K. T. A. S.) marks of the indicator ring ( 12) are located on a bottom side ( 19) of the timepiece ( 1), preferably between the 4 o'clock and 8 o'clock positions.

3. The timepiece of claim 1, comprising a digital time display (6), characterized in that the (K.I.A.S.) marks of the rotatable part (8) of the bezel (7) and the opposed (F. L.) marks of the indicator ring (12) are located on a top side (18) of the timepiece (1), wherein the (F. L.) marks of the rotatable part (8) of the bezel (7) and the opposed (K.T.A.S.) marks of the indicator ring

( 12) are located on a bottom side (19) of the timepiece (1).

4. A timepiece (1) comprising : a case formed of a back cover (2) and a middle part (3), the case being closed by a glass (5); a time display (6); a bezel (7) mounted on the middle part (3) and surrounding the time display (6), the bezel (7) comprising a rotatable part (8) with a circular first edge (9); - a time keeping circuit (10) disposed in the case and controlling the time display (6); and at least one energy source (11) powering the timekeeping circuit (10); characterized in that the bezel (7) comprises Flight Level (F. L.) marks and True Air Speed (K.T.A.S.) marks that are in each case directed radial to the first edge (9) of the rotatable part (8) of the bezel (7) and that are diametrically opposed to each other, wherein the timepiece (1) comprises an indicator ring (12) with a circular first edge (13) that is concentrically arranged with and that is located close to the first edge (9) of the rotatable part (8) of the bezel (7), the indicator ring (12) being fixed to the middle part (3) of the timepiece (1) and comprising Indicated Air Speed (K.I.A.S.) marks and Flight Level (F. L.) marks that are in each case directed radial to the first edge (13) of the indicator ring (12) and that are diametrically opposed to each other in such a way that the (F. L.) marks of the rotatable

S44-0001P-WO2 doc part (8) of the bezel (7) are located opposite the (K. I, A, S.) marks of the indicator ring ( 12) and that the (K. T. A. S.) marks of the rotatable part (8) of the bezel (7) are located opposite the (F. L.) marks of the indicator ring (12).

5. The timepiece of claim 4, comprising an analogue time display (6) with 12 hour positions and with an hour hand (14) and a minute hand (15), and a crown (4) at the three o'clock position, characterized in that the (F. L.) marks of the rotatable part (8) of the bezel (7) and the opposed (K. I. A. S.) marks of the indicator ring (12) are located on a top side (18) of the timepiece (1), preferably between the 10 o'clock and 2 o'clock positions, wherein the (K.T.A.S.) marks of the rotatable part (8) of the bezel (7) and the opposed (F. L.) marks of the indicator ring ( 12) are located on a bottom side (19) of the timepiece (1), preferably between the 4 o'clock and 8 o'clock positions.

6. The timepiece of claim 4, comprising a digital time display (6), characterized in that the (F. L.) marks of the rotatable part (8) of the bezel (7) and the opposed (K. I. A. S.) marks of the indicator ring (12) are located on a top side (18) of the timepiece ( 1), wherein the (K.T.A.S.) marks of the rotatable part (8) of the bezel (7) and the opposed (F. L.) marks of the indicator ring (12) are located on a bottom side (19) of the timepiece (1).

7. The timepiece (1) of one of the preceding claims, characterized in that the indicator ring ( 12) is a part of the bezel (7) and located above the glass

(5).

8. The timepiece (1) of one of the claims 1 to 6, characterized in that the indicator ring (12) is a part of the middle part (3) and located below the glass (5).

S44 0001P WO2 doc

9. The timepiece (1) of one of the preceding claims, characterized in that the rotatable part (8) of the bezel (7) comprises a rubber application (16) attached to at least a part of its circumference ( 17).

10. The timepiece (1) of one of the preceding claims, characterized in that it is embodied as a wristwatch or as a pocket watch.

11. Use of the timepiece (1) of one of the claims 1 or 4 for estimating the true airspeed of an airborne aircraft that is equipped with an altimeter and an airspeed indicator, characterized in that the use comprises the steps of: reading the actual, current Flight Level (F. L.) from the altimeter of the aircraft that previously has been set to standard setting; reading the Indicated Air Speed (K. I. A. S.) on the airspeed indicator of the aircraft; - aligning the actual (F. L.) and (K. I. A. S.) values on a top side (18) of the timepiece (1); finding the corresponding Flight Level (F. L.) on a bottom side (19) of the timepiece (1); and estimating opposite the Flight Level (F. L.) on the bottom side (19) of the timepiece (1) the True Air Speed in Knots (K. T. A. S.).

12. Use of the timepiece (1) of one of the claims 1 or 4 for estimating the expected true airspeed of an aircraft, when on the ground, characterized in that the use comprises the steps of: - lining up the requested Flight Level (F. L.) value and the anticipated Indicated Air Speed (K. I. A. S.) value on a top side (18) of the timepiece (1); finding the corresponding requested Flight Level (F. L.) on a bottom side (19) of the timepiece (1); and estimating opposite the corresponding Flight Level (F. L.) on the bottom side ( 19) of the timepiece (1) the True Air Speed in Knots (K.T.A.S.).

13. The use of one of the claims 11 or 12, characterized in that the timepiece ( 1) is embodied as a wristwatch or as a pocket watch.

S44-0001 P-WO2 doc