Cockpit Voice Recorders for Instructional Flights

Published in the AOPA Flight Training Magazine

A lot goes on in the cockpit during a typical dual training flight. No one has the ability to remember every single item that was learned in the cockpit. A typical student will forget 10% of the lessons learned before the end of the flight. Another 10% will be lost before the end of the day. Only 50% will be remembered after one week. It is simply human nature to forget. Unless the experiences are committed to long-term memory through repetition, these experiences will be short-lived. This is why we take notes in a classroom, and do homework exercises. However, the intense nature of the activities in a cockpit does not lend itself to taking notes. Repetitive exercises in the form of additional training flights are expensive. A cockpit voice recorder is a seldom-used resource that can make an enormous difference to this memory lapse. It can greatly enhance retention and learning. By listening to the recording after each flight, the student will be able to recreate the flight environment in his or her mind. The exact words spoken by the CFI, the verbal expressions of the student and the exchanges with ATC can be reviewed over and over again. The student will be able to return for the next flight with a fresh review of the previous lesson, regardless of how long it has been since the last flight. This can reduce the number training hours for the student. Even the CFI can benefit from listening to his or her own instruction style and improve upon it.

A compact digital voice recorder with an 18-hour recording capacity

We are not talking about cassette tape recorders. These can be awkward and even hazardous in the cockpit. The modern day equivalent of the tape recorder is the all-electronic digital voice recorder. Digital recorders smaller than the size of a cigarette lighter can be bought for as little as $100. They can record several hours of audio, which can then be replayed or downloaded onto a computer. The electronic format has several inherent advantages over its tape counterpart. There is no need to change sides, rewind tapes or make copies. The CFI and the student can both take a copy home without having to run copies. The files can be shared through email or over a website.

A tiny condenser pickup microphone attached to the inside ear cup.

Their compact size is what makes these recorders ideal for cockpit use. They can be conveniently tucked away in a shirt pocket. All that is required is an intercom input. While it is possible to create a wiring arrangement to plug it directly into the intercom system, there is a simpler and less intrusive method. A tiny condenser microphone attached to the inside ear cup of the headset using a small piece of Scotch tape will work just fine without any elaborate wiring. These microphones are available from any electronic supply store for a few dollars. This arrangement does not affect the operation of the headset in any way, and it leaves almost no residue when removed. As long as the microphone wire is very thin, it would not lift the ear cup seal off your skin to create an air gap. The wire can be conveniently wrapped around the headset cord and into your shirt pocket away from the critical areas of the cockpit. This arrangement does not require any special wiring or modification to the intercom system. The whole contraption resides with the headset. Depending on the input sensitivity of the recorder, the microphone may also require a small volume control to prevent overloading the recorder. A little experimentation may be necessary to get it to work satisfactorily.

Critics may question if there really is a need to introduce yet another electronic device in the already crowded cockpit environment. The same question could be asked about GPS, TCAS and the myriad of other electronic gadgets that have proliferated in the cockpit. Every piece of equipment must be weighed with respect to the potential benefit it brings and the level of distraction it causes. Compared to most other equipment in the cockpit, the recorder does not require any attention from the pilot. It is turned on before engine start and turned off after shutdown. The level of distraction it causes is less than that of a transponder squawking VFR.

On the negative side, this technique does demand a significant investment of time from both the instructor and the student. The instructor has to take the time at the end of the day (or at the end of each lesson) to transfer the audio into a computer and send it to the student. The student has to spend the time to listen to the audio. Not every student will have the time or patience for this. However, experience has shown that the students who diligently listen to the audio have a higher retention rate, shaving several hours off their flight training.

Student response on the use of this technique has been very positive. Comments range from “this is an ingenious tool that has helped me a lot” to “I wonder why more instructors don’t use this”. Some students even went as far as purchasing their own recorder so that they could continue this practice after earning their certificates, or to use it with an instructor who does not use this technique.

Here are some hints on what to look for when purchasing a digital recorder. Not all digital recorders have a computer interface. A USB connection that allows fast downloading to a computer is an important feature. Recording capacity also varies greatly from one unit to the next. There are some units that can store as long as 16 hours of continuous recording. Each time the record button is pressed, the recording starts in a new file, which makes it easy to separate the audio files. Some recorders allow the user to organize the audio files into separate folders, just like in a computer system. Another important feature is the Voice Activated Recording (VOR) capability. This allows the recorder to skip over silent periods. For example, a 1-hour flight may only contain 40 minutes of actual conversation or radio chatter. The voice activation will ensure that the silent periods are not recorded. The resulting file will be smaller and easier to review. Some units also have a threshold setting for the voice activation. This is a handy feature because it can be set to the precise level to eliminate the background cockpit noise, just like the squelch control in the intercom system. Battery life can vary significantly, but it is not uncommon to get at least 10 hours of recording with each fresh set of batteries. Due to the small size, most units use AAA batteries, which typically have a shorter life than AA batteries.

These recorders are made strictly for voice recording; so don’t expect high quality stereophonic sound. The average digital recorder samples the audio 1000 times per second. For comparison, compact disc players sample 44,100 times per second. This is what gives them the high fidelity and depth. This is not a shortcoming, as the low sampling rate is more than adequate to capture every salient detail of a cockpit conversation. The recording quality is comparable to what comes out of the intercom. Any higher fidelity in the recorder will simply be wasted effort. Once the audio is downloaded into a computer, it can be transferred into any format using a number of shareware or commercial software. MP3 is one of the most popular audio formats. When encoded as a 16 kb/s MP3 file, one hour of audio can comfortably fit in a 7MB file. This is not an unreasonable size by today’s standards. The file can be transferred to a zip disk or sent over a broadband Internet connection.

This technique works so well that it is surprising why more people don’t use it. It is a small investment with high returns. It can be used even under IFR, as voice recorders as explicitly exempt from FAR 91.21. If the student is conscientious about listening to the audio after each flight, the training time can be reduced by as much as 10-20%. It also helps to preserve the memory and sentimental value of those early training flights in much more vivid detail than a logbook.

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