Characteristics of Piper Aztec

The Piper Aztec can be flown in non-frosting, day or night conditions (VFR and IFR).

table VI.1.1-a : general information on Piper Aztec

Performances

table VI.1.1-b : performances of Piper Aztec

Specifications

table VI.1.1-c : specifications of the Piper Aztec

table VI.1.1-d : Pressure

table VI.1.1-e : Temperature

table VI.1.1-f : Humidity

table VI.1.1-g : other parameters

The other specific instruments described below will be installed in the PIPER AZTEC for the CARBOEUROPE experiment:

The flask sampling consists in filling flask during a flight. The analysis of the samples is made afterwards at he Max-Planck-Institut at Jena. During a flight it is planed that about 12 flasks will be filled up. The time required to fill a flask is about 30 seconds. It is obvious that these data can't be viewed on the quick-look output.

The Non Dispersive Infra Red CONDOR fast CO2 analyzer (Figure 1) was developed in 2001 as part of the European project AEROCARB (Airborne European Regional Observations of the Carbon Balance). The instrument was used in the DLR  Falcon-10 jet for two CAATER campaigns, and is now regularly flying on board a Piper Aztec over the Orléans Forest. The CONDOR is based on a commercial Non Dispersive Infra Red Analyser (Li-COR 6262) doted with a fast response detector and a high acquisition frequency (1 Hz) that make it a dedicated tool for airborne measurements. The performances of the initial commercial analyzer have been improved for bearing temperature and pressure variations encountered during flights, by controlling the temperature, the pressure and the flow rates of gas analyzed by the LI-COR at constant values (Table 1). Atmospheric air is pumped and dried at the entrance of the instrument by a magnesium perchlorate cartridge before being injected into the sample cell.

table VI.1.1-h : Characteristics of the CONDOR analyzer.

In order to be useful for atmospheric research purposes, airborne CO₂ measurements must have a precision better than 0.5 ppm [Gloor et al., 2000]. Frequent calibrations allow ground instrumentation to get a precision of 0.1 ppm. However, flight constraints do not allow to use gas bottles of high volume, therefore calibration is carried out only every 40 minutes and last 6 minutes. In order to take into account slow drifts of the CONDOR analyzer due to changes in surrounding physical parameters such as pressure and temperature, regular calibrations of the instrument have to be done during each flight. This step consists in injecting two standard gases in the analyzer, respectively called the high standard and the low one. Standard bottles were filled in with synthetic air of CO₂ concentration chosen to bracket the atmospheric range for this compound. The low and high standards concentrations have measured in our laboratory on the NOAA scale and are equal to 365.922±0.045 ppm and 401.292±0045 ppm, respectively. Each standard is run during 3 minutes in the analyzer, and only the last minute is kept. The mean and standard deviation are computed to estimate the quality of the instrument. During the CAATER1 campaign, there has been 32 calibrations done, total. The precision of the instrument was always below than 0.18 ppm. This result is highly satisfying, since it confirms that the regulations done on the CONDOR allow to obtain a reproductibility much higher than 0.5 ppm.

The data from CONDOR system are stored on a dedicated acquisition system.

The computing system for acquisition and processing of data embarked onboard the Piper Aztec consists of:

• 1 system of basic acquisition
• 1 scientific station, terminal type X

The main part of Piper Aztec acquisition system is based on a VME bus, and a real time, blade HP processor, functioning under HP-RT system. A lot of charts of acquisition slaves makes it possible to acquire analog signals, frequencies, signals digitized by a CCE box, ARINC data bus, or RS232. Measurements are acquired at frequencies from 1 to 200 Hz. This system is controlled, and supervised from the scientific station, by an engineer of Météo-France. Real-time data are controlled through graphs which allow to control the functioning of the measuring equipment. On board, the data are recorded on extractable hard disk, with copy on magnetic tape (DAT).

Post-flight control

Time series, profiles and airplane trajectory can be available about 2 hours after the landing of the aircraft if landing is at Francazal military airport. These “quick-look” only involve parameters recorded on the basic acquisition system of the airplane.