Narrative:

This narrative describes a low speed event which occurred within 5 to 10 seconds after takeoff. The first officer (first officer) was the pilot flying (PF). The aircraft takeoff weight was approximately 46;500 lbs. With a flap setting of 20 degrees; a trim setting of 7.8; and the use of reduced thrust. The airport weather was clear and the wind was reported at 3 knots; so almost calm. During this event the stick shaker activated and the aural stall warbler tone was heard. In my opinion; the circumstances of the event were induced by the combined effect of an aggressive pitch rate during rotation and encountering significant wake turbulence and propeller slipstream effects from the preceding departing aircraft within 100 to 200 feet above the runway during our initial climb. The following is a detailed description of the pertinent facts and timeline:the aircraft preceding our flight in the takeoff sequence was a bombardier Q400. When the Q400 was cleared for takeoff; our flight was instructed to line up and wait on the same runway. Once we were aligned with the runway and the Q400 was airborne our flight was almost immediately cleared for takeoff. The first officer accepted control of our aircraft and began a reduced thrust takeoff roll. The takeoff roll was normal up to the rotation point. When the first officer began to rotate the aircraft (i.e. Pitch the nose upward); the pitch rate was aggressive and not typical. I would not say that I was alarmed; but I was definitely surprised. The initial climb rate was rapid up to between 100 and 200 feet above the runway at which time we began to encounter significant destabilizing wake turbulence and; I suspect; propeller slipstream effects from the preceding Q400. The turbulence encounter initially induced uncommanded roll excursions of up to 20 degrees left and right. Within roughly 2 seconds after the roll excursions began; the stick shaker activated and immediately after the stick shaker activated the stall warbler tone was heard for 1 to 2 seconds; after which all stall warning indications and roll excursions ceased. So; the entire encounter was perhaps 5 seconds; where the low speed event comprised the last 3 of those 5 seconds. The lowest airspeed I observed during this time was about 15 knots above the low speed checkerboard; but I was not fixated on the airspeed alone; and I believe the airplane continued to climb throughout the event. We continued to encounter definite; but more benign; wake turbulence disturbances through at least 1;500 feet above the runway elevation at which point we entered smooth air.the following are additional items I either noticed or did not notice. (1) in spite of an aggressive takeoff rotation; the aircraft was not pitched beyond the initial command bar guidance designated by activation of the toga button prior to the takeoff roll. (2) the crj fcom states that the stick pusher and stall switch/lights illuminate in conjunction with the stall warbler tone. I did not see the stall switch/lights illuminate; nor did I observe the stick pusher; and the first officer stated to me that he did not feel the stick pusher activate. (3) the first officer stated to me after the event that he had reduced pitch slightly when the stick shaker activated. While I do not question his assertion; I did not perceive his action at the time. (4) during this event; the engine thrust remained at the flex setting which was a deficiency in our response. When the stall warning system activated; it was my expectation that the first officer would increase the engine thrust. However; by the time I realized the degree to which he was focused on manipulating the flight controls in the wake turbulence; the event had passed and aircraft control was no longer compromised. In this situation I should not have waited; but instead I should have immediately advanced the engine thrust to maximum as soon as it became apparent that the PF would not do so. (5) I certainly did not realize; and I believe that my first officer agrees; that the wake and slipstreameffects from a Q400 could be so significant to a crj.I believe that the instability induced by the wake turbulence encounter when combined with the aggressive aircraft pitch rate described previously were together the root cause for the aircraft's stall warning system to activate. I also believe that if these two factors were to have been encountered separately that it is plausible that the stall warning system might not have activated. This is not to discount any personal responsibility in managing the aircraft; but rather to make clear the effect of combined factors. Contributing factors include underestimating the magnitude of aircraft wake compared to the size of the aircraft and therefore being less prepared for a wake turbulence encounter; and being complacent about the professional performance of crew members.I consider the first officer who worked this flight to be professional in the execution of his duties and I have flown with him on many occasions over several years. When flying with a familiar person who also has considerable experience over the same routes and from the same airports; it is easier to adopt the mindset that your coworker will be unlikely to do something which is unexpected. In my case this in turn enhances the chance that I will make a mistake through casual assumptions and failing to 'keep my guard up'. When I asked the first officer afterwards if he noticed that his rotation rate was overly aggressive; he admitted that it could have been; but did not categorically state that it was. From now on I will always take this type of scenario more seriously and address the issue of crew familiarity and its impact on flight safety during the crew briefing where applicable. Through this event I now have a greater regard for the need to apply proactive measure both in discussion and in acting as the pilot monitoring (and PF) based on what I see; and not what I expect.

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Original NASA ASRS Text

Title: CRJ-200 flight crew reported encountering wake turbulence in trail of a Q400 on takeoff from LAX that resulted in a momentary stick shaker.

Narrative: This narrative describes a low speed event which occurred within 5 to 10 seconds after takeoff. The First Officer (FO) was the pilot flying (PF). The aircraft takeoff weight was approximately 46;500 lbs. with a flap setting of 20 degrees; a trim setting of 7.8; and the use of reduced thrust. The airport weather was clear and the wind was reported at 3 knots; so almost calm. During this event the stick shaker activated and the aural stall warbler tone was heard. In my opinion; the circumstances of the event were induced by the combined effect of an aggressive pitch rate during rotation and encountering significant wake turbulence and propeller slipstream effects from the preceding departing aircraft within 100 to 200 feet above the runway during our initial climb. The following is a detailed description of the pertinent facts and timeline:The aircraft preceding our flight in the takeoff sequence was a Bombardier Q400. When the Q400 was cleared for takeoff; our flight was instructed to line up and wait on the same runway. Once we were aligned with the runway and the Q400 was airborne our flight was almost immediately cleared for takeoff. The FO accepted control of our aircraft and began a reduced thrust takeoff roll. The takeoff roll was normal up to the rotation point. When the FO began to rotate the aircraft (i.e. pitch the nose upward); the pitch rate was aggressive and not typical. I would not say that I was alarmed; but I was definitely surprised. The initial climb rate was rapid up to between 100 and 200 feet above the runway at which time we began to encounter significant destabilizing wake turbulence and; I suspect; propeller slipstream effects from the preceding Q400. The turbulence encounter initially induced uncommanded roll excursions of up to 20 degrees left and right. Within roughly 2 seconds after the roll excursions began; the stick shaker activated and immediately after the stick shaker activated the stall warbler tone was heard for 1 to 2 seconds; after which all stall warning indications and roll excursions ceased. So; the entire encounter was perhaps 5 seconds; where the low speed event comprised the last 3 of those 5 seconds. The lowest airspeed I observed during this time was about 15 knots above the low speed checkerboard; but I was not fixated on the airspeed alone; and I believe the airplane continued to climb throughout the event. We continued to encounter definite; but more benign; wake turbulence disturbances through at least 1;500 feet above the runway elevation at which point we entered smooth air.The following are additional items I either noticed or did not notice. (1) In spite of an aggressive takeoff rotation; the aircraft was not pitched beyond the initial command bar guidance designated by activation of the TOGA button prior to the takeoff roll. (2) The CRJ FCOM states that the stick pusher and stall switch/lights illuminate in conjunction with the stall warbler tone. I did not see the stall switch/lights illuminate; nor did I observe the stick pusher; and the FO stated to me that he did not feel the stick pusher activate. (3) The FO stated to me after the event that he had reduced pitch slightly when the stick shaker activated. While I do not question his assertion; I did not perceive his action at the time. (4) During this event; the engine thrust remained at the FLEX setting which was a deficiency in our response. When the stall warning system activated; it was my expectation that the FO would increase the engine thrust. However; by the time I realized the degree to which he was focused on manipulating the flight controls in the wake turbulence; the event had passed and aircraft control was no longer compromised. In this situation I should not have waited; but instead I should have immediately advanced the engine thrust to maximum as soon as it became apparent that the PF would not do so. (5) I certainly did not realize; and I believe that my FO agrees; that the wake and slipstreameffects from a Q400 could be so significant to a CRJ.I believe that the instability induced by the wake turbulence encounter when combined with the aggressive aircraft pitch rate described previously were together the root cause for the aircraft's stall warning system to activate. I also believe that if these two factors were to have been encountered separately that it is plausible that the stall warning system might not have activated. This is not to discount any personal responsibility in managing the aircraft; but rather to make clear the effect of combined factors. Contributing factors include underestimating the magnitude of aircraft wake compared to the size of the aircraft and therefore being less prepared for a wake turbulence encounter; and being complacent about the professional performance of crew members.I consider the FO who worked this flight to be professional in the execution of his duties and I have flown with him on many occasions over several years. When flying with a familiar person who also has considerable experience over the same routes and from the same airports; it is easier to adopt the mindset that your coworker will be unlikely to do something which is unexpected. In my case this in turn enhances the chance that I will make a mistake through casual assumptions and failing to 'keep my guard up'. When I asked the FO afterwards if he noticed that his rotation rate was overly aggressive; he admitted that it could have been; but did not categorically state that it was. From now on I will always take this type of scenario more seriously and address the issue of crew familiarity and its impact on flight safety during the crew briefing where applicable. Through this event I now have a greater regard for the need to apply proactive measure both in discussion and in acting as the pilot monitoring (and PF) based on what I see; and not what I expect.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.