V i s i t o r   r e s p o n s e s 

According to your web site, when the craft turned and moved in the direction of the witnesses, it was at a distance of 1 km (0.62 mile or 3,280 feet), a distance that can be measured on the scaled map....  read more 

In this case, an Army officer, Lt. Col. AMOND [now retired], and his wife, stopped their car on what Wim [VAN UTRECHT] describes as a "lonely road" and wound down the window with "ears pricked" to try and detect any sound from an object of evidently large angular size showing details of lit "panels" or windows as well as various other separate lights which circled apparently nearby for up to 8 minutes.....  read more 

It is correct that an inversion will refract sound towards the surface, and the recommendation to avoid flying in an inversion makes sense therefore. But the inference that flying above the top of an inversion will have the inverse effect of abnormally refracting sound upward is unwarranted I think.....  read more 

Re the Ernage case in particular and silent helicopters in general, I looked a bit further into the sound propagation question and helicopter noise sources. Perhaps this will help us decide the merits of the theory. Anyway I've collected some information for future reference - and just because it's interesting.....  read more 

I'd like to point out that Mr. PAQUAY treats Lt. Col. AMOND's "2x moon diameter" light as relating to the angular size of a light source, when clearly this should be treated as an impression of the circle of glare (overloaded retina) caused by this "huge" and "brilliant" light shining into the witness's face......  read more 

I would like to correct the approach of Mr. PAQUAY who claims that the observation of the "spotlight" was made while the craft was 1,000 m from my observation point. This is COMPLETELY WRONG.......  read more 

In his response, dated June 5, 2008, Col. AMOND claims that my distance estimation of 1,000 m for the phase during which the craft turned towards him is completely false and that the real distance at that moment was 100 to 200 m. He also disputes my calculations and qualifies them as unscientific.......  read more 

The Belgian airspace is surveyed by four powerful radars, two military and two civilian, which are all interlinked, i.e. any duty controller can select the image of any of these radars at any one time. All radar registrations are recorded and these recordings are kept during a well determined period......  read more 

A little comment about the strawman argument at the end of Wilfried DE BROUWER's email......  read more 

In my opinion, the important information in DE BROUWER's e-mail is not in his last paragraph about the reliability of Col. AMOND. Of course human testimony is not always reliable, but Jean-Michel ABRASSART tends to say that it's NEVER reliable. I think he pushes his argument too far here, turning it into some kind of indisputable doctrine.....  read more 

Now I am beginning to wonder : how could it be that the four Belgian radars did not detect these objects in the sky which were neither aircraft nor helicopters...  read more 

Gen. DE BROUWER's first-hand testimony confirms not only that no helicopter should have been flying (as previously reported by Col. AMOND) but that, in point of fact, no illicit helicopter or other aircraft was detected by radars covering the area....  read more 

I will try to contribute to this debate by sharing with you that I have the following documents concerning the Ernage case:

(1) A "note" of 2 pages with an additional 3 pages of drawings sent by Ir. André AMOND, LtCol. BEM, to the Cabinet of the Minister of National Defence on December 19, 1989. This text was published in Inforespace No. 80 (April 1991) and in Vague d’OVNI sur la Begique (p.90-91).

(2) A standard SOBEPS questionnaire filled out by André AMOND on January 3, 1990.

(3) Another questionnaire filled out the same day by his wife.

(4) A detailed report compiled on January 9, 1990 by a mathematically minded investigator in the formal style of a SOBEPS rapport d’enquête. This report presents in a separate way what Col. AMOND told the investigator and what his wife told him. There appeared to be only one, but very instructive difference. Later more about that.

On June 17, 2008, J.P. PHARABOD asked if the published drawings on page 92 of VOB were made by Col. AMOND [this question from Jean-Pierre PHARABOD is not included in our visitor responses - WVT]. The answer is yes for the Figures 2.22a and b, as well as 2.23, but the map in Figure 2.21 has been slightly modified with respect to the original (the SOBEPS report contains the map that provided the basis for Figure 2.21). To avoid further possible confusions, I add a copy of this map to the present mail. I extract the following explanations from the report.

The Ernage case. The object was discovered by Col. André AMOND on December 11, 1989, at 18:45 in position 1 (surrounded on the map by a circle). The car of the witnesses was then in position A (surrounded on the map by a triangle). Actually, he saw only a row of four white-yellowish luminous trapezoidal surfaces of decreasing size and below them a nearly hemispherical red light of pulsating intensity. He saw no object that carried these lights, but they were moving with fixed positions relative to one another. They were slowly moving towards the south at very low altitude, and remained in view until they disappeared behind a row of trees near the farm of Sart-Ernage. These trees are presented as green dots on the map. Also indicated on the map is the azimuth which changed from 295° to 250°.



The map that accompanied Prof. MEESSEN’s response. It appears to have been drawn by SOBEPS investigator J. LAURENT shortly after his interview with Col. AMOND. The map published in Vague d’OVNI sur la Belgique is an adapted version of this map. Distances and scale are respected, but in the book version several indications are blackened, probably for better reproduction. (WVT)

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Col. André AMOND was accompanied by his wife, who also saw the object at her right side immediately after her husband told her to look over there. It is important to note, however, that right from the beginning (in position A) she could discern a dark shape (une forme sombre), under which there was the pulsating red light. This difference can be attributed to the fact that the colonel was wearing coloured correcting glasses for far vision. His wife was not. The investigator noted in his report that the reactions of the witnesses clearly indicated that they had not deliberated in advance to tell the same story. Besides this difference, which proves that there was indeed an object, although dark and not easily recognized, everything fits well together.

I attach the sketch that Col. AMOND made of the ensemble of lights, i.e. when the object passed behind the two first trees. The trees were clearly visible at the horizon and had no leaves, since this happened in December. The colonel estimated the apparent height of the object as being about 2/3 the height of these trees. The object was thus very low above the horizon. Its apparent length was about equal to the separation of the two first trees, but its true distance was unknown. The colonel saw the light again when he arrived at B. Then he stopped at C, which is the highest point on this street. He stopped the engine, but did not extinguish the lights of the car. His wife opened the window at her side, and both witnesses continued to observe the phenomenon, which was still moving at the same altitude and at low velocity. The trajectory of the "object" can only be estimated, but it seemed to be linear and the object passed between two wooded areas (position 2).

Col. AMOND was astonished that he heard no sound coming from the object, although he pricked up his ears. He was also amazed by the fact that the light of the moon, which should have been reflected by the object, didn’t make it visible. The surface of the object remained dark and actually invisible to the colonel. The object moved from point 2 to 3 in about 3 to 4 minutes. When it arrived at 3, in front of the wood, which is indicated as a green patch on the accompanying map, it turned towards the car and directed a very luminous beam in its direction. Since the light became brighter and larger, the object came closer, but it remained lower than the tops of the trees behind it. The wife of the colonel became frightened and told him to start the car, which he did.

The car responded without any problem, but the object made a manoeuvre and raised, nose up. It distinctly showed its lower face now, but the colonel saw only three uniformly illuminated, white circular surfaces of equal diameter and a large circular, pulsating red light. The centres of the white lights seemed to form an equilateral triangle, but the dark surface of the object that carried them was oblique. The upper circular white light was (3 to 4 times) more intense than the two other circular white lights. At the centre of this triangle, there was the large red light that they had previously seen from the side. Its diameter was 2 to 3 times larger than the diameter of the white circles. The object then regained its previous position, so that the red light was again underneath. It then disappeared rapidly towards the south.

The diameter of the approaching light beam was very big (about two times the diameter of the Moon), but my personal opinion is that this doesn’t allow a determination of the diameter of its source. The light being too brilliant for that. The investigator writes that the light was "dazzling" ("éblouissant"). The actual distance at closest approach (between 4 and C) was also difficult to evaluate. Any calculations would thus lead to a pseudo-scientific precision, but subjective impressions should be recorded. According to Col. AMOND, the centres of the white lights were possibly separated from one another by 6 to 10 m. The actual values are not as important as the relative disposition of the four lights and the absence of sound, although the object had to be quite close and was flying at low altitude. During a reconstruction, the investigator used his chronometer to determine the total duration of the sighting. He found 10 minutes, but the phase during which the object approached with the dazzling beam in front and the one during which the bottom side appeared lasted respectively only about 30 seconds and 30-40 seconds. This description clearly excludes the helicopter hypothesis, invented by someone who was a priori convinced that this object shouldn’t be considered as a true UFO.

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Gen. DE BROUWER’s mail of June 22 provided important complementary information, since it stated that four powerful, interconnected radars didn’t detect anything that was flying there and specified that no conventional object was allowed to fly between sunset and sunrise. Since a moving helicopter would have been detected, even at low altitude, the conclusion of the investigations of the Belgian Air Force is that the Ernage case, as well as the other reported sightings of November 29 and December 11, 1989, "cannot be attributed to a helicopter or any other aircraft." Gen. DE BROUWER adds that "Colonel AMOND is a highly qualified and very reliable person, the major elements of his testimony are consistent and there is no reason why he should be discredited."

J.M. ABRASSART reacted (on 23/6) in a rather astonishing way. He finds it "annoying" that UFO proponents don’t understand that "UFO skeptics say that EVERY human testimony is unreliable". Mr. ABRASSART adds that "There is nothing specific to one individual" that "DE BROUWER is not a qualified psychologist" and that "the scientific literature tells us that every human testimony is unreliable, no matter who we are." This is an extraordinary claim, requiring extraordinary proof. Grégory GUTIEREZ responded (the same day) by saying that, although human testimony is not always reliable, to assert that "it’s NEVER reliable" is pushing the argument too far. Martin SHOUGH concluded (also the same day) that given the lack of proof "and the previous difficulties encountered with the helicopter theory, I would like to propose (...) that the theory should now be withdrawn as untenable (for all practical purposes) unless further specific evidence can be found". "I suggest that attention should be focused on other possibilities", Mr. SHOUGH added.

I certainly agree that it is necessary to sort out unrealistic claims, but that doesn’t mean that all UFO sightings have to be discarded and that all witnesses are unreliable. Martin SHOUGH wrote (also on June 23) that "science cannot be allowed to rule human experience out of consideration" and "à propos Ernage, it would be perverse to claim that an army Col.'s familiarity with helicopters is irrelevant to assessing his certainty that he did not see a helicopter. Witnesses are imperfect measuring instruments, but it remains possible that as a group their reports may contain information about physical phenomena with which we are ourselves unfamiliar". He provided more reflections that are pertinent for our discussion, and noted in particular that an asymmetric treatment of human testimony, attributing higher weights to observations that are in favor of the privileged hypothesis and "zero weighting" to those that yield opposite results, simply isn't objective".

Jean-Pierre PHARABOD noted (that same day) that "Now I am beginning to wonder: how could it be that the 4 Belgian radars did not detect these objects in the sky which were neither aircraft nor helicopters? There is a futuristic, but not unphysical possibility: plasma stealth". He provides a very interesting reference in this regard. I have to add that the main result of my investigation of radar detection during the Belgian UFO flap was that we can be sure that it is extremely difficult to detect these objects through the scattering of microwaves. Some kind of stealth technology had to be involved. The problem of making ships and aircraft undetectable by means of sound and EM waves (visible light, infrared light or microwaves) is extremely important for military engineers (see "Invisibility rules the waves", Physics World, March 2008).

I got interested already some years ago in searching a physical explanation of the fact that some UFOs seem to have the capacity to make themselves optically invisible. I spoke on the phone with a German military pilot who, in the seventies, while flying his star-fighter jet (F-104G), made three "interceptions" of the same UFO. They did correspond to a frontal approach, so that the UFO passed the plane at very close range. He always had a clear radar image, but he never saw the object. The ground radar was also unable to detect it. The airborne radar was not yet of the Doppler-type, but it tracked the object in a continuous and coherent way. Since stealth technology of radar waves can already be realized by using flat surfaces and absorbing paint, the really new feature results from the apparent capacity to become optically invisible. Some authors mentioned in the UFO literature that occasionally, these objects can change their form or seem to appear or disappear where they are, as if they had the capacity to materialize or dematerialize. Allen HYNEK mentioned a case where the disappearance was progressive (like the Cheshire cat in Alice in Wonderland). I also heard of a stationary UFO that disappeared, as if it was moving a veil in front of it.

A single observation of this type would be unimportant, but a group would raise a question concerning the underlying technology. We should then try to find out a possible explanation. Is it possible to modify the refractive index in the vicinity of the object, so that light rays are deviated in such a way that they bypass the object by resuming their initial directions of propagation, as if no object had been there? There may be other possibilities as well. Anyway, the Ernage case is not the only one where the actual object was not easily detected by the naked eye.

Auguste MEESSEN
Hamme-Mille, Belgium

[Auguste MEESSEN studied at the Science Faculty of the Catholic University of Louvain (UCL), Louvain-la-Neuve, Belgium. From 1960 till 1962, he was a research associate at the U.S. Massachusetts Institute of Technology. After that, he became a professor at UCL, where he teached quantum mechanics, theoretical and mathematical physics, solid state physics and didactics of physics. He became a professor emeritus in 1996 and continued to do research in various fields. Prof. MEESSEN, now retired, was also an important member of the Brussels UFO group SOBEPS. His personal web site with numerous papers on the UFO subject can be found at www.meessen.net.]

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Our reply :

Following Gen. Wilfried DE BROUWER’s reaction of June 22, Martin SHOUGH asked (on June 23) if it would be possible to reach a consensus and focus on explanations other than the helicopter theory. In principle that would be okay for us, but we think that to abandon the theory altogether at this point, as Gen. DE BROUWER and Prof. MEESSEN suggest, would be a mistake.

Let’s not forget that, despite the damage already inflicted on the helicopter theory, several of the reasons why we proposed this explanation in the first place still remain intact. First there is the general aspect of the reported object, and in particular the luminous panels (which can be interpreted as windows), the white lights and the pulsating red light (which are typical of normal aircraft), and the bright light in front of the object (which strongly resembles a helicopter searchlight). Secondly, there is the manoeuvrability of the object, and in particular the almost complete turn close to the ground which a helicopter is perfectly capable of executing.

Apart from the general aspect of the unknown object, our personal experience with a "silent" helicopter (described in "Our reply" to Martin SHOUGH’s response received on April 20), and the fact that our country went through a UFO hype at the moment (causing many people to report ordinary aircraft as UFOs), we had noticed that helicopters were barely mentioned in the official statements issued by the BAF about the Belgian UFOs. Also, ufologists and sceptics alike had never taken any action in this regard. And finally, our own efforts to try to find out if helicopters could have been responsible for some of the key sightings had produced nothing either (letters to pilots were left unanswered and e-mails to the Army’s information services suffered the same fate).

In November 1996, CAELESTIA’s photo and film analyst Jan VAN EETVELT asked us to prepare the draft of a Parliamentary question which his father, Representative Jozef VAN EETVELT, would be prepared to address to Mr. PONCELET, our country’s Minister of Defence at the time. We readily agreed and thought it would be a good idea to include a question about an incident which had occurred some 7 hours after Col. AMOND’s sighting in a village called Jupille-sur-Meuse, close to Liège. More specifically, we asked if the Defence Minister had any information that could help elucidate this spectacular incident (a helicopter and military personnel were said to have visited the area the day after). The response was somewhat different from the reaction we received from Gen. DE BROUWER on June 22. This is what our Minister of Defence stipulated with regard to the sightings that occurred between December 2 and 18, 1989 (we translate from French):

"After examination, it is impossible to make a correlation between the visual sightings and certain parasite radar echoes that are often generated by thermal inversion. This inversion was present during most of the sightings. (...) When flying at night, VFR flights [Visual Flying Rules - WVT] are only authorized for helicopters. Other airborne vehicles are obliged to introduce a flight plan according to the IFR (Instrument Flying Rules)".

Apart from this last sentence there was no mention of helicopters in the Minister’s reply (the rest of the text focused mainly on the F-117A, RPV, ULM and AWACS aircraft).

On December 8, 2002, in an attempt to help French investigator Renaud LECLET with a paper he was preparing on the Belgian UFOs and helicopters, we decided to send a letter to Gen. DE BROUWER asking him if there was still a way to find out if there had been a helicopter in the air during the night of Col. AMOND’s sighting. We never got a reply.

So, by 2003 there was still nothing conclusive that allowed us to rule out the presence of a helicopter in the southern part of the country on the night of December 11-12, 1989. Convinced that everything possible had been done, Renauld LECLET decided not to wait any longer and to include the Ernage incident in his analyses of the Belgian wave. In his text, he supported the idea that the object seen by the colonel and his wife had been an army helicopter. Renaud then tragically passed away. Four years later, I published a summary of the case on the CAELESTIA website, hoping it would finally produce some useful feedback.

When in October 2007 Roger PAQUAY’s calculations suggested that Mr. AMOND had underestimated the distance to the object and overestimated the object’s size, the helicopter explanation seemed even more solid. However, in April 2008, the theory suddenly lost ground when Martin SHOUGH reacted on this forum with an elaborate series of notes on helicopters and sound propagation.

Now, in June 2008, two new statements have been made that seem to torpedo the helicopter theory once and for all : one by Col. AMOND himself, stating that, at one point during the sighting, the unidentified object was only 100 to 200 m away from his car, and another from Gen. Wilfried DE BROUWER, stating that no helicopters were in the air that night. But before we are prepared to put the theory to rest, we would like to see some points cleared up first.

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(1) Regarding Col. AMOND’s claim that the object came to within 100 to 200 m of the car

Mr. PAQUAY based his calculations on the map that accompanied our article. This map is a stylized, but loyal, version of a map published on p. 92 of Vague d’OVNI sur la Belgique, where it is labelled as Fig. 2.21. Drawn on this map is the presumed path followed by the object. Since the path is drawn on a scaled, printed map, we assumed it to be accurate. Measured on this map, the object appears to have come within a distance of about 830 m from the parked car (Mr. PAQUAY used a distance of 1,000 m, i.e. the approximate distance from the car to the centre of the circular path).

However, on June 5, Mr. AMOND stated that the object came to within 100 to 200 m of the car, not 1,000 m.

Following this statement, we pointed out to Col. AMOND (on June 13) that the distance he now mentioned was not corroborated with the object’s flight path as indicated on Fig. 2.21. On June 15, Mr. AMOND replied, that this map was "absolutely NOT accurate". To emphasize this, Col. AMOND send us a PowerPoint presentation (a link to an updated version can be found further down this text) with on p. 2 the map in question accompanied by the following comments :

"Free-hand sketch provided in 1989 for:
1. General Information
2. Idea of the geographic places (between ERNAGE and GEMBLOUX)
3. Description of the different stages
 - Sketch NOT accurate at all
 - Made out of mind
 - Without going into details
 - Map support NOT correct".

As the discussion unfolded it became clear that Col. AMOND had placed the wrong map next to the above quoted text and that, probably, he had another sketch in mind, namely Fig. 2.23 in the SOBEPS book. This illustration is indeed a free-hand sketch made from memory and without the help of a map. It’s obvious that such a sketch cannot be used for measuring distances.

But what then with the much more detailed Fig. 2.21, the one we used for our web site article? Was it accurate or not?

From Prof. MEESSEN’s response we understand that Fig. 2.21 was based on a map drawn by SOBEPS investigator J. LAURENT shortly after his interview with the two witnesses. Like Figure 2.21, this early document (published above) shows community boundaries, printed titles, and much detail. The object’s trajectory appears to have been carefully drawn and azimuth bearings are included for different phases of the observation. If we are to measure the closest distance between the car and the unknown object on this original document, we get 800 m, which is close to 830 m, but still very different from "100 to 200 m".

Yet, even with regard to this map, which indirectly also formed the basis for Mr. PAQUAY’s calculations, Col. AMOND now tells us (via an e-mail received on July 4), that this map too is ?NOT accurate? and that the details in the SOBEPS report that deal with distance, altitude, trajectory and size do not tally with the information he provided to the SOBEPS investigator. This is odd because we have rarely seen a UFO investigative report with a more detailed map than the one provided by Mr. LAURENT. Prof. MEESSEN seems to be taking our side on this, since he explicitly tells us that this map is "very detailed" and "compiled by a mathematically-minded investigator". Also, this must be the first time in history that a UFO investigator places the reported UFO at a greater distance than the witnesses believed it was.

On June 18, Col. AMOND sent us a new version of his PowerPoint presentation. Fig. 2.21 is still there (along with the erroneous caption) but added is a page 8 with a panoramic view of the sighting location photographed from the spot where the car was parked. Indicated on the photo is the path followed by the object as seen from the car. It confirms that the object emerged from behind a block of trees and then descended below the tree tops of another group of trees and turned towards the witnesses (there was a temporal confusion about this too). More importantly however, the PPT also includes a new map. This time the object’s flight path is traced on a Google Earth map. Surprisingly, the circular part of the trajectory now stretches to within only 80 to 100 m of the parked car...

By way of comparison we made the following illustration showing the presumed flight path as drawn by the SOBEPS investigator in early 1990 (blue arrow) next to the flight path as presented in Col. AMOND’s recent PowerPoint presentation (yellow arrow). The position where the car was parked is marked with a red "x". Measured on this Google Earth map, the distance between this spot and the point of closest approach is 800 m on the 1990 SOBEPS map, and only about 100 m on Col. AMOND's recent PPT map.



In the light of these conflicting estimates, it is unfair to label Mr. PAQUAY's calculations "pseudo scientific". All Mr. PAQUAY did was rely on the best available evidence, namely the map we published and which was based on a carefully executed and detailed drawing made by a (mathematically-minded) investigator shortly after the event. When 18 years later, one of the witnesses offers previously unpublished estimates that suggest a much more spectacular "close encounter", it is only normal that reservations are being made.

There can be only one conclusion from all this, namely that there is no certainty about the distance of the object when it completed the 270° turn. All we know is that, at a given moment, the object descended in front of a block of trees in the background that is located at 1,400 m from the spot where Col. AMOND stopped the car.

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(2) Regarding Gen. DE BROUWER’s statement that "none of the four Belgian radar stations had registered any traffic that could have caused this phenomenon"

The way this sentence is phrased makes it essentially meaningless as it still doesn’t tell us whether or not a helicopter or a small airplane had appeared on the radar screens at the time of the sightings. From Gen. DE BROUWER’s statement, one is inclined to infer that traffic was registered, but that the person who verified the registrations didn’t think this traffic had anything to do with the reported UFOs. If that was indeed the case, we for one would like to know what was registered exactly and why it was considered irrelevant in explaining the reported phenomena. Was it because the radar returns were easily identified as ordinary aircraft, because they appeared too far away from the UFO hot spots, or because they were identified as irrelevant "parasite radar echoes" caused by a thermal inversion, as mentioned in the response to our Parliamentary question quoted above?

But there’s another reason why we are reluctant to put the matter to rest.

Gen. DE BROUWER claims that no aircraft were in the air, not in the evening of December 11 and not in the evening of November 29, 1989 (the day the Belgian wave began). Yet, Mr. PAQUAY himself informed us that, on November 29, 1989, he and his son were standing on the second floor of the hospital at Seraing, near Liège, when both saw how several Mirage jets were flying on and off the air base of Bierset (Bierset being 7 km NNW of Seraing and 41 km west of Eupen city where the majority of November reports emanated from). This happened shortly after 5 p.m. on November 29, 1989. The jet planes first headed southwest (following the orientation of the landing strip), then turned to the hospital with the white light on the front landing gear clearly visible, and finally executed a large circle. Two hours later, just before 7 p.m., Mr. PAQUAY was on a road near Hognoul (4.5 km N of Bierset) when two Mirage jets passed at low altitude over his car. He could clearly see their typical triangular shape and the flashing lights on the wingtips. The jets were flying towards the north-northeast and it would have taken them only 5 minutes from Hognoul to Eupen. Was Gen. DE BROUWER informed of these flights? Were they not mentioned because they were thought to be irrelevant?

So we’re still not entirely sure whether we should abandon the helicopter theory completely (personally, I would rather store it in the fridge for a while). Still, our reservations should not keep us from examining other possibilities, and we agree with Jean-Pierre PHARABOD that, in doing so, we should also take into consideration the other reports collected for December 11-12.

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Re your reply to Prof. MEESSEN, you're right, the statement about flight plans in the Defence Minister's reply to the Parliamentary question is different from what we understood Gen. DE BROUWER to say....  read more 

Thanks for Mr. PAQUAY's follow-up. I was not (as Mr. PAQUAY believes) suggesting that Col. AMOND was "dazzled" to explain a large image. As he says, an "overloaded retina" is not a very good explanation....  read more 

Allow me to clarify a few points. 1. Your statement: "A helicopter is perfectly capable of executing such a manoeuvre". The report of André AMOND suggests that the object was making a tight turn with a considerable angle of bank (45 degrees?) at very slow speed (20-30 km/h?)....  read more 

I don't claim to have the detailed aeronautical experience of General DE BROUWER, but during my own military service, I did have some exposure to helicopters as a passenger and as an observer from the ground.....  read more 

Thanks for your input Joe. Yes, clearly it can happen that when the conditions for sound propagation and other witness circumstances are unfavourable people can fail to hear helicopters......  read more